^''%. °% 



^o^ 









. ^* 



.is *^ 









cJ>^ * 



..^' 






^. -0' 



.\s 










v^^ 



.:^^^ >. 









.0' 



O- aC 



.'b^ -^ 



% 








^^^-^"^ 












,aV -. 


f^%c^ 



.r^^ 



v^ '^ 



t - 1 



'^^^'^s 






^0■ 



V * ^ ■^ \> 



.^ ^ ^^ 



N^"s 












Al 







x^'^^ 



American Telegraphy. 



AMERICAN TELEGRAPHY 



AND 



ENCYCLOPEDIA OF THE TELEGRAPH 



SYSTEMS, APPARATUS, OPERATION. 

EMBRACING 

ELECTRICAL TESTING; PRIMARY AND STORAGE BATTERIES; DYNAMO 
MACHINES; MORSE, DUPLEX, QUADRUPLEX, MULTIPLEX, SUBMARINE, 
AUTOMATIC, AND WIRELESS TELEGRAPHY; BURGLAR-ALARM, 
FIRE-ALARM, AND POLICE-ALARM TELEGRAPHY; PRINT- 
ING TELEGRAPHY; MILITARY AND NAVAL SIGNALING; 
RAILWAY BLOCK SYSTEMS ; TELEGRAPH WIRES, 
CABLES, AND CONDUITS ; ETC. 



BY 

WILLIAM MAVER, Jr., 

MEMBER OF THE AMERICAN INSTITUTE OF ELECTRICAL ENGINEERS ; EX-ELECTRICIAN BALTIMORE AND 
OHIO TELEGRAPH COMPANY; AUTHOR OF MAVER'S "WIRELESS TELEGRAPHV." 



668 PAGES, - - - 490 ILLUSTRATIONS. 



NEW YORK: 

MAVER PUBLISHING COMPANY. 

1909. 



LIBHARyofGOMeRESS 



Ont 



vv!j^ ?iet;eiVed 






COPYRIGHT, 1892, 1896, 1903, 1908, 

By WILLIAM MAVER, Jr. 



PREFACE 



Somewhat less than twenty-five years ago the simple Morse system of telegraphy 
was the only one in general use in America. One or two printing telegraph systems 
were in operation, and attempts were being made to utilize, satisfactorily, chemical au- 
tomatic telegraph systems. At that time, although the duplex system ot telegraphy 
was in limited use, it had not been perfected, and in some quarters it was looked upon 
as a " scientific toy," *' very beautiful in its way but quite useless in a practical point 
of view." 

Since then the duplex and quadruplex systems, and the Wheatstone automatic tel- 
egraph system, have been extensively introduced into the commercial telegraph service 
of this country. Since then, also, multiplex, phonoplex, burglar alarm, police signal 
and other analogous systems of telegraphy have been invented and placed in success- 
ful operation. Many important improvements in printing telegraphy, submarine tele- 
graj^hy, fire alarm telegraphy, etc., have, in recent years, also been introduced, and in 
numerous other ways the art of electrical telegraphy has been advanced. 

While a number of the systems and improvements referred to have, at different 
times, and at more or less length, been described in electrical books and periodicals, the 
writer is not aware that even a majority of them has been fully described in any one 
book, and thus a knowledge of them placed within easy reach of the ordinary student of 
telegraphy. " 'v • ., 

Believing that such a book would be of value, the attempt has been made, in the 
present work, to supply a comprehensive account of the systems of telegraphy now in 
use in America, and as such an account naturally includes sources of electromotive 
force employed, line construction, line and apparatus testing, etc., those subjects 
have also been dwelt upon at some length. 

As far as possible each subject has been treated from a practical standpoint, and 
the book, as a whole, has been written in a manner intended to be clear to novices in 
electrical matters, more especially those who are directly engaged in the practical 
working of electrical systems of telegraphy. To that end, where it has seemed essen- 
tial to a proper understanding of a subject, full, and, it is hoped, accurate, explana- 
tions of laws and facts of electricity and m:igiietism involved in the operation of sys- 
tems and methods described, have been given. In short, the object, however imper- 



vi PREFACE. 

fectly carried out, has been to provide in this work a complete practical hand-book 
of telegraphy. 

With but few exceptions the systems herein described are in actual operation. 
The exceptions relate to peculiar types of systems, a description of which was con- 
sidered desirable for reference. In nearly every case the diagrams employed have 
been designed expressly for this book. 

The author thankfully acknowledges his obligations to numerous friends for 
valuable practical information concerning a number of the systems herein described, 
and through their courtesy in that respect many details of certain systems are now 
given for the first time. 

PREFACE TO FIFTH EDITION. 

Advantage has been taken of tlie opportunity offered by the publication of the 
present new and much enlarged edition to add somcAvhat to the title of this work. 
This change has been suggested many times by friendly critics, it having been 
observed that the original title appeared to convey the idea, to those unfamiliar with 
its scope, that the work was confined to a treatment of Morse telegraphy, and per- 
haps some of its allied branches, whereas, in fact, the book is encyclopedical, 
treating not only of all that virtually appertains to telegraphy proper, but also of 
fire-alarm, police, burglar- alarm, and printing telegraphy; railroad block-sigualing; 
manufacture of telegraph wire ; electrical testing, etc. , etc. 

It was originally iutended to limit this work to descriptions of systems in actual 
operation in this country, but in order that the book may now, as far as practicable, 
conform to its amplified title, descriptions of a number of telegraph systems, 
repeaters, etc., used in other countries have been added, together with descriptions 
of telegraph systems of recent application in this country and abroad, such as wire- 
less telegraphy, etc. In many other ways, also, as by the sections on inductance, 
impedance, Gray's harmonic telegraph, the telautograph, etc., the author has 
endeavored to enhance the usefulness of the work as a book for students and as a 
work of reference, to which endeavor he has been in a measure prompted by the 
increasing use of the work by students generally, and as a text-book of Telegraph 
Engineering in colleges and other institutions of learning. 

It may be noted that since the first edition of this work was printed over 
90 pages of new matter (comprising about 60,000 words of text) and 60 illus- 
trations have been added, mainly in the present edition. For synopsis of new mat- 
ter see Supplemental Index, last page. 

The author takes this occasion to express his appreciation of many kindly words 
which have reached him commendatory of this work, and would add that communi- 
cations concerning subjects treated of herein are cordially invited. 

18,8 Arlington Avenue, W. M., Jr. 

Jersey City, N. J. 



CONTENTS. 



Page 
Introductory. , , , . . . * , ' • . , i , . xii 

CHAPTER I. 

ELECTRICITY. I 

Theories, Electrical Terms, Etc. 

CHAPTER II. 

PRIMARY BATTERIES. 9 

Polarization.— The Gravity or Callaud Cell —The Care of,— The Use of Oil on. — Hydrometer.— 
The Leclanche Cell. — The Fuller Cell. — Chloride of Silver Cell. — The Edison-Lalande 
Cell. — The Burnley Dry Cell. — The Gassxer. — Arrangement of Cells in BATrERiES.-=»Cells 
in Series. — Cells in Multiple. — Cells in Opposition, Etc., Etc. 

CHAPTER III. 

THE DYNAMO MACHINE IN TELEGRAPHY. 27 

Introduction of in Telegraphy. — Joint Resistance of Circuits. — Distribution of Current In Divided Circuits, — 
The Dynamo-Electric Machine.— Theory of.— Methods of Arranging Dynamos in Telegraphy.— 
Western Union Arrangement, — Dynamo Reversing Switches. — Postal Arrangement, — Arrangement for 
Locals.— The Motor Dynamo.— The Storage Battery, Etc., Etc, 

CHAPTER IV. 

THE MORSE TELEGRAPH SYSTEM. 50 

Theory. — Operation of, — Closed Circuit Method. — Open Circuit Method. — Telegraph Codes, — Steno Tele- 
graphy. Etc., Etc.— Practical Notes for Beginners. 

CHAPTER V. 

MORSE TELEGRAPH APPARATUS. 58 

Keys.— Bunnell.— Steiner. — Victor,— Legless,— Self-Closing- - Relays,— Main Line — Pocket.— Pony— Box. — 
Sounders. — Local. — Bunnell — Western Electric — Victor. — Main Line Sounders, — Winding of 
Etc. — The Morse Register. — Ink Recording Morse Register.— Automatic Paper Winder. 
— Automatic Telegraph Sender. — Telegraph Transmitters — La Dow Transmitter. — Typewriter in 
Telegraphy. — Bunnell Sounder Resonator. — Switch Boards, — Main Office, — Single Spring Jack 
Boards. — Way Office Switch Board. — Way Office Cut Out.— Lightning Arresters, Etc. 

CHAPTER VI. 

THE CONDENSER,— STATIC CHARGE,— DISTRIBUTION OF, ETC.— INDUCTION, MUTUAL, 

SELF, ETC.— THE RHEOSTAT, 90 

Adjustable Condenser. — Standard Condenser — Wheatstone Condenser. — Condensers Arranged in Multiple. — In 
Series —Electrification.— Static Charge,— Mutual Induction Between Parallel Wires, Etc.-^ 
Inductance, Capacity, Reactance, Impedance, Loaded Conductors, Rheostat. 

CHAPTER VII. 

GALVANOMETERS. 

Theory.— The Tangent Galvanometer.-^ Parallelogram of Forces. — Western Union Tangent Galvanometer.^ 
Astatic Galvanomet'ers.— Detector Galvanometek.— Tuomson Reflecting Galvanometer.— Shunts,— 
Directing Magnet.— D'Aksonvall Galvanometer.— Table of Tangents'. 



CONTENTS. 
CHAPTER VIII. 

ELECTRICAL TESTING. 122 

The Wheats tone Bridge.— Theory.— Post Office Pattern.— Siemens Pattern.— Measuring Resistances.— 
By Wheatstone Bridge Method— By Substitution Method. —Capacity Tes is.— Measurements Elec- 
tromotive P'ORCE.— Internal Resistance of Batteries. — Locating Faults o\ Telegraph Wires. — Lo- 
cating Crosses. — A Wheatstone Bridge Method. — 'Locating Faults by Varley Loop Test. — By Capacity 
Test, — Measuring Insulation Resistance of Wires and Cables.— Direct Deflection Method. — 
Measuring Partial Insulation Resistance of Telegraph Wires. —Testing Insulators, Etc. 

CHAPTER IX. 

THE DELANY LINE ADJUSTMENT. 350 

CHAPTER X. 

AUTOMATIC TELEGRAPH REPEATERS. 153 

Button Repeaters.— Woods. — Aittomatic Repeaters.— The Maver-Gardanier.— The Neilson. — Multiple. — The 
Milliken.— The Horton.— The Weiny.— The Atkinson..— The Ghegan.— Open Circuit.— Double Current. 

CHAPTER XI. 

DUPLEX TELEGRAPHY. 169 

Differential Method. — Bridge Method. — The Stearns Duplex. — Continuity Preserving Transmitter, — Spark 
Coil. — Static Compensating Condensers. — Balancing Stearns Duplex. — The Polar Duplex. — Operation 
of.— Pole-Changer. — Polarized Relay. — Theory of Polar Duplex. — Balancing the Polar Duplex. -Terminal 
Connections, Etc. 

CHAPTER XII. 

THE QUADRUPLEX. 194 

Theory of.— Operation of.— Edison Quadruplex. —Moment of No-Magnetism in Neutral Relay.— Smith Con- 
denser Arrangement. — Ratio of Current Strength, Transmitter Closed and Open. — Action of Condenser as. 
Static Compensator,— Terminal Connections VV. U. Quadruplex. — W. U. Neutral Relay, Winding of.— 
Combination Rheostat —Repeating Sounder, Etc. — Dynamo Quadruplex Key Systems. — W. U. or 
Field Dynamo Key System, Theory of. — Terminal Connections W. U. Quadruplex.— Postal Telegraph 
Company Quadruplex. — Quotation Company^ Quadruplex. — General Remarks.— Nomenclature. — 
Balancing The Quadruplex. — Causes and Symptoms of Faults on Duplex and Quadruplex Circuits and Meth- 
ods of Detecting Them.— The Roberson.— The British P. O. Quadruplex. 

CHAPTER XIII. 

DUPLEX AND QUADRUPLEX REPEATERS. 241 

Extended Locals. — Quadruplex-Shcrt Wire Automatic Repeaters.— The Downer. — Gardanier— Emergency Re- 
peaters. — Multiple Quad-Short Wire Repeaters. — Quad-Single Wire Automatic Repeaters, — The Ed- 
ward's. — Waterbury. —Arrangement for Converting Short \Vire into Main Line Wire. — Hints ON THE 
Management of Quadruplex-Single Wire Repeaters, Etc. Etc. 

CHAPTER XIV. 

BRANCH OFFICE SIGNALING DEVICES. 256 

Tne Buzzer or Interrupter. — New York Branch Office Call Wire. — Chicago Branch Office Signal. 
Arrangement. — The Hurd Branch Office Call. 

CHAPTER XV. 

LOOP SWITCHES. 261 

Loop Switch Connections. — Postal Loop Switch.— Davis Loop Switch. 

CHAPTER XV]. 

COMBINATION DUPLEX SYSTEMS, ETC. s6a 

The Edison-Smith Duplex. — The Sieurs Duplex. 



CONTENTS. ' ^^ 

CHAPTER XVII. 

SUBMARINE TELEGRAPHY. 267 

Mirror Receiver.— The Thomson Siphon Recorder.— Tlie Cuttriss Magnetic Siphon Recorder.— Earth Currents. 
—Use of Condenser in Connection Therewith.— Simplex Working.— Duplex Working.— Stearns Arti- 
ficial Cable.— Muirhead i^rtificial Cable.— Steakns Cable Duplex.— Muirhead Cable Duplex.— Bal- 
ancing Cable Duplex.— Rate of Signaling.— Brown and Allen Relay.— The Jacobs Duplex.— Under 
Water TELECRArHY.— Brown Cable Relay Repeater. 

CHAPTER XVIII. 

AUTOMATIC TELEGRAPHY. 287 

Rapid Automatic Telegraphy.— Single Current.— Double Current Methods.— Chemical Automatic 
Telegraph Systems.— Theory.— Chemical Solutions Employed.— Effects, Etc.— Anderson Chemical 
Automatic System.— Page and Line Chemical Recorder.— The WnEATsroNE Automatic System.— 
Perforator. — Transmitter, — Theory of, Etc. — Wheatstone Receiver. — Wheatstone Duplex. — Terminal Con- 
nections, Etc. — Wheatstone Automatic Repeaters. — Condenser. — Repeater Relay. — Winding of. — Dial 
Rheostat. — *'Extra Current" Neutralizer.— Balancing and Adjusting Wheatstone Apparatus, Etc. — 
Automatic Fac-Simile Telegraphy.— Methods.— Electro-magnetic— Chemical. — Thb Denison 
Fac-Simile System.— Stevens Perforator.— Delany Rapid Automatic— Electrograph.-Pollak-Virag Automatic. 

CHAPTER XIX. 

WRITING TELEGRAPH SYSTEMS. 

Writing Telegraph Company System.— The Robertson Transmitter.— Receiver.— The Etheridge Transmitter.— 
Writing Telegraph Central Office. — The Telautograph. 

CHAPTER XX. 

WIRELESS TELEGRAPHY. 
Phelps, Edison, Preece, Marconi, De Forest. 

CHAPTER XXI. 

SYxNCHRONOUS MULTIPLEX TELEGRAPHY. 
Theory of.— Delany System — Synchronizing Device, Etc. 336 

CHAPTER XXII. 

THE TELEPHONE.— SIMULTANEOUS TELEGRAPHY AND TELEPHONY.— VARLEY-ATH- 
EARN DIPLEX-DUPLEX.— THE EDISON PHONOPLEX. 

The Telephone.— Theory of.— Simultaneous Telegraphy and Telephony.— Van Rysselberghe System, 
— Varley-Athearn Duplex- Diplex.— Superposed Currents.— The Edison Phonoplex. — The Phone,— Mag- 
netic Coil, Etc.— Gray's Harmonic Telegraph. 

CHAPTER XXIII. 

TIME TELEGRAPH SERVICE. 356 

Time Telegraph Signals. — Electrically Synchronized Clocks. — Barkaud and Lund Regulator. — Hamblet 
Synchronizing Apparatus. f > 

CHAPTER XXIV. 

HELIOGRAPHY.— MILITARY TELEGRAPH SIGNALING. 361 

Heliography. — MacGregor's Heliograph.— Operation of, Etc. — Military Telegraph Signaling. — Field 
Equipment. -Flag and Flash Signaling. — United States Station and Field Kits, Code, Et,-. 

CHAPTER XXV. 

THE AMERICAN DISTRICT TELEGRAPH MESSENGER SERVICE. 367 

Call Boxes.— Central Office, Box Circuits.— Return Signal Call Boxes.— The Van Size.— District Service 
Magnet Bell.— Double-Pen Register. — Self-Starting Register. — Multiple Call Boxes. — Field and Firman. — 
District Service Switches. — The Lockwood Battery, — District Service Time Slips. — Faults on Dis- 
trict Circuits. 

CHAPTER XXVI. 

AUTOMATIC BURGLAR ALARM TELEGRAPHY. 3S1 

The Holmes Burglar Alarm System.— Operation of, Etc.- The Wilder Duplex Aupomatic Burglar 
Alarm. — Operation of, Etc.— Combination Call and Burglar Alarm Box. — The Double Balanced Relay. 



X CONTENTS. 

CHAPTER XXVII. 

PRINTING TELEGRAPHY. 390 

Theorv " Step by Step " Svstems.— News Tickers. -" Gold and Stock " Ticker System. —Theory and Ope- 
ration ©f. Transmitter Key Boar..— Shifting Ue\nce.— Scott Two Wire Tickek.— Phelps Stock 
Prin'ier. — Operation of.— Pap r Fee-'.— Shifting Device —Key Board.— Type-Wheel.— Unison.— The 
" Umyersal " OR Edisox Tickek System.— Operation of.— •' Universal " Transmitter.— New York 
Quotation Company Ticker System — Operation. — •' Locker" Circuit — Healy Clutch Device. — Shifting 
Apparatus.— Ticker.— Paper Feed.— The Phelps "Motor" Priniing Telegraph System.— Printer — 
Motor Governor. — Transm'tting Apparatus. — Receiving Apparatus,— Synchronizing Device.— L'nison De- 
vice-Adjustment, Etc.— The Es.ick Page and Line Printek.— Theory.— Paper Carriage.— Printing 
Apparatus.— The Buckingham, Barclay, Murray, Hughes. Rowland. Baudot Systems. 

CFIAPTER XXVIII. 

FIRE ALARM TELEGRAPHY. 437 

.Hwple Fire Alarm Telegraph Circuit.— The Gamewell Fire Alarm Telegraph System.— Automatic Non- 
Interfering Repeater. — Theory of, Etc. — Gardiner Non-Interfering Street Box, with Auxiliary Fire Alarm 
Attachments. — Indicator. — Operation of. — The Gaynor Fire Alarm Telegraph System. — Of)eration 
of. — Manual Repeater, Etc.- -Jersey City or Spkicher Fire Alarm Telegraph System.— Operation 
of. — Tower Bell Circuit Connections. — Tower Bell Electro-Mechanical Striking Apparatus. — Thk Game- 
well Auxiliary Fire Alarm Telegraph System. — Operation of. — "Cross" Relav. — "Disturbance" 
Relay. Etc.— Automatic f lite Ai.akm TsuiGitAPiii.— The Bulen System.— Operation of —Thermo— 
stdts,Etc 

CHAPTER XXIX. 

POLICE SIGNAL TELEGRAPH SYSTEMS. 47i 

The Gamewell Police Signal Telegraph System.— Central Office, Street Box Electrical Connections.— 
Operation of, Etc.— Stable Electrical Connections.— Automatic Transmitter, or Multiple Break- Wheel.— 
Street Boxes. -The Chicago Police Patrol Telegraph System.— Operation — Patrol Box. — The 
Pearce and Jones Police Patrol Telegraph System. — Signal Box. — Stover Special Alarm De- 
vice. — The Municipal Police Signal Telegraph. — Street Boxes. — Time Stamp. — Answer Back Sig- 
nal, Etc— Police Patrol Boxes. 

CHAPTER XXX. 

RAILWAY ELECTRIC BLOCK SIGNALING SYSTEMS, ETC, 494 

THE Union Switch and Signal Electro-Pneumatic Block System.— Operation of. Etc.— The Union 
Switch and Signal •' Clock'" System.— The Hall Railway Signal System. — Operation of, Etc.— 
Hall's Electric Signal for Crossings. — Overlapping Block Signal System.— The Sykes System 
OF Block Signaling.- The Stewart-Hall Train Order Signal.— Train Signals.— The Hart 
Train Signal.— ^Iolor Operated Semaphores— Miller Cab Signal. 

CHAPTER XXXI. 

OVERLAND TELEGRAPH WIRE. 509 

The Manufacture of Iron and Copper Wire.— Wire Drawing.— Galvanizing Iron Wire.— Mechanical 
Tests of Telegraph W ire. — Wire Gauges. — American Standard Wire Gauge. — Micrometer, or Pocket 
Gauge — Tests for Breaking Strain. — For Ductihty.— Wire Testing for Resisiance and Conductiv- 
ity. — Effects of Impurities On. — Corrections for Temperature. — Table of Co-Efficients for. — Weight 
Per Mile Ohm. — Iron and Steel Line Wire, Terms, Etc. 

CHAPTER XXXII. 

UNDERGROUND CONDUITS.— UNDERGROUND. AND RIVER AND HARBOR TELEGRAPH 

CABLES, ETC. 524 

Underground Conduits. — ''Drawing In and Out." — •• Solid."— Rodding.— Underground Telegraph 
Carles. —Cable Jointing. — Measuring Insulation — Resistance of Joints. — River and Harbor Cables. — 
Cable Testing.— Remarks Concerning. — Elecrification. — Locating Faults in Cables Electro-me- 
CHANiCALLY. — Poiut to Point Method. — Locating Faults in Short Under-Water Cables. — L'nder-Runnine 
Method, Etc. 



CONTENTS. yj 

CHAPTER XXXIII. 

CONSTRUCTION AND MAINTENANCE OF TELEGRAPH LINES. 524 

Line Construction.— Erection of —Tools, Etc.— Guying.— Pole Lightning Arresters-— Brackets.— Cross- 
Arms.- Pins.— Fetter Drive Screw.— Insulators.— Wirk Stringing.— Wire Barrow.— Come Alongs.— Ty 
ing- Wire to Insulators.— Joints on Aerial Wires.—" Sleeve " Joints.— Pliers,— Anti-Hum Device.— Hou-e- 
ToP Fixtures. — After Construction. — Maintenance of Lines — TreeTrimming.— Etc. — Line Repair 
ing, Etc. — Trouble Hunting. — Af rial Cables. — Methods of Suspending. — Aerial Cable Hanger. — Chin- 
NOCK Cable Winder. — Operation of, Etc. 

CHAPTER XXXIV. 

SPECIFICATIONS-ESTIMATES— MISCELLANEOUS— TABLES. 553 

Sp2cifications for Apparatus. — Battery Material. — Hard Drawn Copper wire. — Iron Wire. — Aerial or Undt-r 
ground Cable. — Short, River or Harbor Cable. — Emergency Cable. — Form of Contract Specification (■ ' 
Manufacturing and Laying of Underground Cable —Miscellaneous. — Binding Screws.— Message ' ■ 
Prices of Telegraph Apparatus, Material, Etc- — Effects of High Temperatures on Vulcanized India Ruhi 
Insulation — Tables. — Difference Between Principal Wire Gauges in Decimal Parts of an Inch, — Numb<= 
Diameter, Weight, Length and Resistance of Commercial Copper Wire,— Wages of Operators. 



I N T FiO 13 TLJ CTT O I^^i', 



HE word " telegraph '■ strictly defined means " to write afar off." In the modern 
practice of telegraphy, however, the term has a wider meaning and it is 
now used to signify any means whereby intelligence is conveyed to a distance by 
signs or sounds. 

From remotest times methods of communicating intelligence to a distance 
have been employed for purposes of war, defence and extraordinary intercourse. 

A brief review of some of the earlier methods may be of interest at the open- 
ino- of a work of this nature, especially as such a review may be found to show that 
principles involved in the operation of very primitive methods of telegraphing 
have been applied in more or less modified forms in some of the modern electrical 
telegraph systems. 

The ancient Greeks employed among other methods of telegraphing one which 
was, perhaps, the simplest of all the ancient methods. This method required the 
erection of tow«'S on hill-tops and other elevations, suitable distances apart. In 
each tower a vessel capable of holding a given quantity of water was placed. Down 
the side of the vessels the letters of the alphabet were arranged. Each vessel was 
supplied with means for permitting the water to flow out of the vessel at a given rate. 
When ready for signaling the vessels were filled with water. The station de- 
siring to signal the other, raised a torch, at night. This was responded to by a 
similar signal from a distant tower. At another signal the attendants in each 
tower withdrew the stops and permitted the water to flow out of the vessels, and when 
the Avater had fallen to a point opposite a desired letter the torch was again raised; 
the attendant in the receiving tower noted the letter; each attendant refilled the 
vessel and the operation was repeated until the message was completed. 

Towards the latter part of the eighteenth century the semaphore system of 
telegraphy was introduced; the term semaphore signifying " A Sign I bear.'' 

In semaphore systems of telegraphy one or more movable arms or levers 
supported on suitable posts are employed. By the manipulation of these levers 
messages may be transmitted with moderate rapidity. This method of telegraphing 
was very widely adopted, and, for many years, utilized, throughout Europe, especially 
in France and Russia, and is, in a modified form, in use to day on every i-ailroad in 
the world. 



Xiv AMERICAN TELEGRAPHY. 

In this country a semaphore system was for many years in successful operation 
"between Sandy Hook and New York, before, and for a short time after, the introduction 
of the electric telegraph, or, as it was termed, the magneto telegraph. 

The semaphore company had stations on this line at Sandy Hook; the Highlands, 
N. J.; at Staten Island and in the cupola of the Custom House, New York City. This 
line was intended chiefly for reporting the arrivals of vessels at Sandy Hook. 

For some time after the establishment of the magneto telegraph between New 
York and Sandy Hook the S"emaphore system held its own, for, while in foggy and 
hazy weather both systems were useless, since passing ships could not be discerned, 
in wet weather, without fog, the semaphore system was often the first to convey 
marine intelligence to the city, owing to the poor insulation of the electric telegraph 
wires. The semaphore company, however, ultimately found it to its interest to unite 
with the electric telegraph company. 

Another system of telegraphy, somewhat akin to the semaphore, and known as 
Washington's telegraph, was at one time employed in this country. It was presum- 
ably so called because of the fact that it was one among many similar telegraph sys- 
tems used during the war of Independence in this country. 

The apparatus used in the Washington telegraph system was easy of construction^ 
and, it must be admitted, somewhat crude. It consisted of a portable mast, on the 
top of which was placed a tub, or barrel; also, on one side of the post, a movable flag 
was placed, and on the other side, near the top, a basket, which was suspended from 
a bracket or nail. By interchanging the position of the flag the barrel and the bas- 
ket, and by moving the flag up and down, various signals could be sent, — about 60 
different signals in all. 

Although up to 1852 certain visual systems of telegraphy such as the semaphore, 
were in extensive use, electricity had been utilized, experimentally, long prior 
to that date, as a means of communicating intelligence to a distance. 

For example, Lesage, of Geneva, had constructed a telegraph system consisting 
of 24 line wires, one for each letter of the alaphabet. At each terminal of each wire 
pith balls were suitably suspended, and, taking advantage of the well-known repellant 
effect that follows the electrification of such light substances, Lesage had succeeded, by 
the use of frictional electricity applied to the wires, in transmitting intelligible signals 
over them. 

In 181 5 an "alphabetical " telegraph was invented by Francis Ronalds. In this 
arrangement, clockwork, operating a revolving dial, was used at each end of a wire. 
The dials rotated in unison. A notch was cut in each dial. Behind each dial the 
letters of the alphabet were placed in a circle, so that as the dial revolved one 
letter at a time was seen through the notch. Pith balls were electrically connected 
with the wire at each end. At a certain signal the clockwork was started, and as the 



INTRODUCTORY. XV 

notch came opposite a desired letter the circuit was so operated that the pith balls 
were actuated. The letter at that time seen through the opening in the dial was noted 
aud in that way messages were transmitted. 

In 1839 a telegraph system was devised by de Heer in which a physiological 
effect of the electric current was employed. In this system ten wires were utilized be- 
tween the sending and receiving stations. At the receiving station the operator 
placed his fingers and thumbs on the ten terminals of the line wires. Thus the pas- 
sage of a current through one or more of the wires was felt in the fingers touching 
those wires, and signals were indicated by a pre-arranged manner of transmitting cur- 
rents through the wires. For example, a simultaneous " shock " in the thumb of the 
right hand and forefinger of the left hand might signify the letter A, etc. 

In 1774 Yolta discovered that electricity could be generated by chemical means, 
and, availing of the "voltaic" current from a battery, efforts were made, more or less 
successfully, between 1806 and 1830, to utilize, in the transmission of telegraphic 
signals, its property for decomposing metallic salts, by causing electric currents origin- 
ated at one terminal of a wire to decompose a chemical solution at the other termi- 
nal; these efforts were the pioneers of others more successful in later years. 

In 1820 the discovery was made by Oersted that a magnetic needle would be de- 
flected from its normal position when held parallel to a wire conveying an electric 
current, and, further, that the deflection was to the right or left according to the direc- 
tion of the current. Taking advantage of these discoveries various needle telegraph 
systems came into existence and were at one time extensively employed in Europe^ 
and are still in limited use there. 

The needle systems were operated on the principle just referred to; namely: that 
a current flowing in a wire would deflect a magnetic needle. A magnetic needle 
was pivoted in the centre of a coil or coils of wire, and a pointer, attached to 
the needle, swung in front of a dial. Deflections to the right or left signified certain 
letters. These deflections were produced by sending over the wire pulsations of one 
polarity, or alternations of both, as required by the letter to be transmitted. 

In 1824, Sturgeon, of England, discovered that when a current of electricity is 
caused to flow in an insulated wire surrounding a bar of well annealed iron, the lat- 
ter becomes a magnet, and that when the current ceases to flow the iron at once 
loses its magnetism. 

Availing of these electro-magnetic laws, Morse, in 1837, invented the telegraph 
system which bears his name, and which system, in one form or another, is, 
to-day, in almost general use. 

The apparatus first used by Morse in his experiments bore but slight resemblance 
to the instruments now employed in Morse telegrapliy. For instaiu^e, the modern 
Morse relay weighs about 3 J pounds. The first telegraph relay or electro-magnet con- 



XVI AMERICAN TELEGRAPHY. 

etructed for Morse weighed over 300 lbs; and it was tliought that the height of im- 
provement was reached when a relay was made that weighed only 70 lbs. By degrees, 
however, the laws of electro-magnetism became more clearly understood, and, finally, 
the instruments reached their present shape and size. 

Much of the subsequent work of telegraph engineers up to the present time has 
related to the improvement of apparatus and the development of means for increasing 
the capacity of the existing wires either by the use of "automatic " telegraph systems 
or by the aid of " multiplex" systems of telegraphy. 

It is not, however, only as an agent in the transmission of commercial or social 
telegrams that electricity is now employed in telegraphy. It also performs an in- 
dispensable part in the operation of Fire, Police, and other analogous telegraph sys- 
tems, many of which will be found described iu the unabridged American Telegraphy. 



AMERICAN TELEGRAPHY, 



CHAPTER I. 
ELECTRICITY. 

THEORIES ELECTRICAL TERMS ; ETC. 

As with but few exceptions tlie systems of telegraphy rlescrlbecT in this book are 
electrical a reference to some of the theories of electricity may properly be made 
here. As, however, an extended review of the various theories of electricity (and 
magnetism) would be outside the scope of this work, such reference will be limited to 
what may be termed '* working theories," and to those throngli which several of 
the common terms at present in use have been introduced. 

Reference will also be made here to some of the more important laws of electricity 
involved in the operation of the systems to be described ; reference to other electrical 
and also to certain magnetic laws and actions will be made elsewhere as may seem 
appropriate. 

It may be ])remised that nothing is, at present, definitely known of electricity, ex- 
cept through its manifestations as a force, which manifestations are, it is assumed, the 
results of some mode of motion or disturbance of, or around the molecules of the sub- 
stances in Avhich tlie manifestations are exhibited. The same may be said, generally, 
of magnetism, Avith this, additionally, that magnetism is always either an accompani- 
ment of, or a result of, electrical action. 

It is well known that electricity may be manifested in many ways; for example, 
by rubbing a glass rod with dry silk, or by rubbing a stick of wax with dry flannel, 
Avhen those substances become " electrifled ' ' and capable of attracting small, adjacent 
bodies. It is known, also, that when thus electrified, if the glass and the wax be lightly 
suspended they will attract each other, while, if two pieces of wax or two pieces of glass be 
thus electrified and similarly suspended it is found that they repel each other. 

Since /^;r^ may be defined " as any cause whicli moves a body that is at rest or 
stops it when in motion," or which retards or increases the velocity of a body in mo- 
tion, the foregoing may serve as simple instances of electricity as a force. 

Franklin considered that electricity was an imponderable "fluid," pervading every- 
thing, and Avhich, in its normal condition, Avas uniformly distributed in all substances. 
He assumed that the electrical results obtained by rubbing glass were due to the produc- 
tion of an excess of the electric fluid in that substance, and that those obtained by rub- 
bing the wax were due to a diminution of the fluid. The electricity manifested in the 
glass, when rubbed by silk, he called "positive; '' that in the* wax, when rubbed bv 
wool, he termed " negative." 

The FrankUn theory was for many years entertauied, but the idea of electricity as 
a "fluid " is now o:enerallv abandoned. 



2 AMERICAN TELEGRAPHY. 

For practical purposes it may be assumed, that all substances possess an electric 
state wliich is normally zero or neutral, and that, while in that condition, no electrical 
phenomena are ':ipparent; but if that normal electrical condition of ths substance be 
disturbed, electrical manifestations result. 

This assumption may be iliustrated by analogy. For example, air, it is known, at 
any given portion of the earth's surface, is under a certain pressure, reckoned in so- 
many pounds per square inch at sea level. Normally, so far as any given section of the 
earth's surface is concerned, if the air be left undisturbed, there is no visible evidence 
of its existence. If, however, by any means, as by the heating of the air particles at 
some one point of the earth's surface, the normal pressure is disturbed, a "'current" of 
air, that is, wind^ is the result, and the observed effects of wind are, obviously, manifes- 
tations of air in motion. Further, when, by suitable means, an excess of air is drivea 
into an air chamber, the compressed air within the chamber acquires a tendency to es- 
cape therefrom by any available outlet, and, if such an outlet be provided, a perceptible 
current of air will flow until equilibrium is established, that is, until the pressure with- 
in the chamber is equal to that without. If, on the contrary, a A'acuum be created in 
the chamber the reverse will be the case; the tendency will be for the air without to^ 
enter the chamber, until, as before, equilibrium, or zero pressure, is established. In 
either case, it will be observed, the direction of the current is from the point of higher 
to the point of lower pressure. 

In the case of Rii " electrified '' body, that is, one in which the normal, electrical 
condition may be supposed to have been disturbed, it may be assumed that the mole- 
cules of the substance resist or oppose the changed electrical condition, and, furtheiv 
that, when thus displaced, the tendency of the molecules is to return to the normal 
condition of zero or neutrality; as, for example, an archer's bow resists bending. and> 
upon being bent, tends to restore itself to its normal condition. 

If the electrified body be surrounded by an " insulating" medium, analogous, for 
instance, to the w^alls of an air chamber, a 23re!5c5ure is presumably exerted on that me- 
dium, which pressure will be relieved when the electrified body is, so to speak, given an 
opportunity to resume its normal condition of electrical equilibrium, as will be the case 
when a so called conductor of electricity is provided, for, example, an iron or copper 
wiie. 

If, reverting to the air analogy, means for maintaining the vacuum or pressure in 
the air chamber, and a suitable inlet and outlet, be provided, and if the inlet and outlet 
be then connected by a pipe, it is apparent that a current of air will flow from the point 
of greater to the point of lesser pressure, continuously. 

Analogously, if means are taken to renew the electric stress or pressure of the 
electrified body as quickly as it may be relieved, what is termed, a "current " of elec- 
tricity will " flow" continuously in the conductor. 

Such a " current " is obtained when, for example, the terminals of a common vol- 
taic cell are connected by an iron or copper wire. It is known that the terminals of the 
plates of such a cell are " positively " and " negatively " electrified as, for instance, in 
the case of rubbed glass and wax. 

When the plates of such a cell are thus joined, it is found that the connecting wire 
now possesses peculiar properties; one of which is that a magnetic needle suitably sus- 



ELECTRICAL TERMS. ^ 

^lended parallel to the wire, is steadily deflected from its usual position. This 
Reflection of the magnetic needle is one of the best known manifestations of the 
-electric current. 

More recently a theory termed the electronic theory has been developed, accord- 
ing to which theory, briefly stated, the material atom instead of being indivisible, 
-as has been held for nearly a century, is made up of an equal number of positively 
4ind negativelj charged electric units, termed electrons. In short, that elections aie 
•electricity, and therefore the ultimate particles of matter are electrical. According 
to the theory of the ether as developed by Dr. J. Larmor, it possesses a rotational 
■elasticity, the various parts of which resist complete rotation round an axis, yet may 
1)6 displaced or sheared over each other. The strain by which this displacement is 
^Drought about is due to an electric force, and it disappears when the electric force 
as withdrawn. In such an ether the electron is the center of a permanent strain- 
2-)oint which can be moved about in this ether as a kink can be moved in a rope. 
The ether can only be moved by the electrons and it only car move them. Hence 
it has been said that the electrons have a grip of the ether and by their rapid motion 
set up and are affected by radiation in the ether. The size of the electron as com- 
2mred with the material atom is exceedingly small, there being, it has been calcu- 
lated, about 700 in the smallest known atom, that of hydrogen, and about 140,000 
in one of the densest, the mercury atom. These atoms are assumed to be in orbital 
rotation around each other, and notwithstanding that the diameter of the mercury 
atom is taken as the one one-hundred-millionth of a meter, the orbits of the 140,000 
electrons constituting the atom are relatively as great, proportional to their size and 
to the space in which they move, as are those of the planets of the solar system. To 
account for the phenomena of current electricity by this theory it is supposed that 
in addition to the electrons composing the atoms of substances there are many so- 
called free negative electrons intermingling and interchanging with the electrons of 
the atoms. These free electrons under an electric force seem able to move unob- 
structedly through metals or other good conductors, giving rise to the electric cur- 
rent and its accompanying magnetic field, whereas the structure of non-conductors 
is apparently so complex the electrons cannot move freely through them. That 
^vhich has hitherto been regarded as positive or negative electricity (constituting a 
charge of electricity) is due to the removal of a negative electron from an atom, 
which latter thereupon becomes positive; a theory which to this extent conforms to 
Pranklin's fluid theory, the exception being that what he termed negative electricity 
is known to be positive electricity, and vice versa. By this theory, also, an alter- 
nating current in a conductor is due to oscillations of the electrons, and the elec- 
trons in rapid vibration in a conductor give rise to electrical waves in the ether. 

The reader will find a more detailed treatment of this subject in the authors 
"Wireless Telegraphy.'' See also ''Hertzian Waves," Chapter XX. 



POTENTIAL ; ELECTROMOTIVE FORCE ; CURRENT ; RESISTANCE. 

For practical purposes it may be considered that when a body is "positively' 
electrified it has acquired an electrical condition above the normal, or zero, and 
2 



4 AMERICAN TELEGRAPHY. 

when it is electrified " negatively,' ' that it has acquired an electrical condition below 
the normal. 

It is then essential to adopt a standard by which to estimate the extent of that 
electrification, either above or below normal; as, for example, in the case of the meas- 
urement of temperature, zero may be taken as that degree of heat or cold which exists at 
the freezing point of water, temperatures above or below that point being referred to 
as so many degrees above or below zero. 

In the case of electricity, the zero pressure or condition is takeii as being equal to 
that of the earth ; it being assumed that the latter, in common with other bodies, has 
at any given point, a normal electrical condition. Thus, when a body is said to be posi 
lively or negatively electrified it is assumed to be electrified above or below the nor- 
mal electric state, condition or " level" of the earth. 

The technical term used in relation to electric pressure is " potential," but 
the terms "potential" and " pressure,'' are now, almost generally, used interchange- 
ably. 

" Potential " is defined as " power to do work," or " capacity for doing work." 
For instance, if a weight be raised by any means from the earth's surface against 
the attraction of gravitation, say, one foot, it is said to have acquired and to possess a 
potential or capacity for doing work, equal to the energy which it was necessary to ex- 
pend in raising it to that height. Analogously, when, by any means, whether by a 
voltaic cell, friction, or otherwise, electricity is excited in a substance, for instance, a 
wire, it is said to have acquired an electric j^otential, that is, a capacity for doing 
electrical work. 

The force, whatever it may be, that produces this electric ])otential is frequent- 
ly termed electromotive force, that is, the force which moves or drives electricity, 
and this force is measured by the extent to which the electric potential of a body is 
brought above or below zero; that is, again, the difference of pote?itiaI or pressure ex- 
isting in the electrified body. It is also said, disregarding the cause which develop?* 
this difference of potential, that the difference of potential, itself, constitutes the 
electromotive force, that is, the force which moves electricity, virtually as the flow or 
movement of water in a pipe connected with a high reservoir is said to be due to ih^ 
*'head" of water; that is, the difference between the pressure of water in the reservoir 
and that at zero level. It is, however, definitely known that when a so called " differ- 
ence of electric potential " is established between any two points of a conductor, that 
which is termed an electric " current,'' flows, and will continue to flow as long as the 
difference of potential is maintained. 

It is assumed, for convenience, that when a body acquires a "positive " potential, 
the tendency of the current is downwards towards zero, and that when it acquires a 
" negative " potential, the tendency of the current is from zero to the point of lower 
potential. 

The more frequently used terms relating to electrical measurement are potential, 
electromotive force, current and resistance. 

All substances are capable of conducting electricity. Some, however, possess this 
property so limitedly that, by comparison with certain other substances, they may be 
considered as not possessing it and are, consequently, termed non-conductors, insula- 



ELECTRICAL TERMS. 5 

tors or dielectrics, while tliose substances which are capable of conducting electricity 
freely are said to possess conductance, or conductivity,and are termed conductors. 

There is, on the contrary, no material known which does not offer some resistance 
to the " passage" of electricity through it, the extent of which resistance yaries in dif- 
ferent materials, and it also yaries with the size of the conductor of a giyen material : 
decreasing as the size or weight is increased, and increasing as the size is decreased. 

In the case of all things that are measurable, units of measurement are necessary. 
Thus the unit of weight, English measure, is the pound; the unit of length is the foot 
or yard, etc. 

As electricity is also measurable, instances of which will be noted later, 
suitable electrical units of measurement are necessary and haye been jDroyided. Thus, 
the "practical " unit of electromotive force is the yolt; the practical unit of current 
strength is the ampere; the practical unit of resistance is the ohm. The derivation 
of these units will be alluded to subsequently. 

The volt represents a certain potential to which electricity is brought, above or be- 
low zero potential, as, analogously, one foot may represent the difference of pressure 
between a volume of water at sea level and another volume raised one foot above 
sea level. 

The difference of potential between the plates of a voltaic cell, such as the well 
known gravity cell, is slightly more than one volt. 

The term electromotive force is frequently abbreviated thus: e. m. f., and in for- 
mulae is represented by e. These abbreviations will be occasionally employed herein. 

The *ohm is equal to the electrical resistance of a column of pure mercury .00155 
square inch sectional area (that is, the area of a section of the column taken directly 
crosswise,)and 41 73 inches in length at a temperature of 32°F. 

Perhaps, to some, a clearer, if a less exact idea of the value of the ohm, as a 23rac- 
tical unit of resistance, may be conveyed by considering that it is equal to the resistance 
of one mile of pure copper wire about twenty-three one hundredths of an inch, that is, 
slightly less than one-quarter of an inch, in diameter, at a temperature of 60°F. 

One mile of ordinary galvanized iron, six-tenths of an inch in diameter, has a re- 
sistance of, approximately, one ohm. 

With a giveii electromotive force the current which will flow when a conductor is 
provided will be proportional to the resistance or, as it is sometimes termed, the " op- 
position/' which the conductor may offer to the passage of the " current." 

The ampere is defined as the strength of current which flow^s in a conductor, or the 
amount of electricity that will be driven past any given point of a conductor, when the 
electromotive force is one volt, and when the resistance of the conductor is one ohm. 

The resistance of a conductor of given dimensions is, generally speaking, constant^ 
regardless of changes in the electromotive force or in the current. 

ohm's law. 

The current strength in a conductor yaries directly with changes in the electro- 
motive force ; it yaries inversely with changes in the resistance. 

This very important law of the electric current, now so well known, is termed, 
Ohm's law, after its discoverer. The law nmy also be thus stated; the current 

' * See Chapter XXXf. ~~ 



6 AMERICAN TELEGRAPHY. 

strength., expressed in amperes, in any circuit, is equal to the quotient of the electro- 
motive force in volts, divided by the total resistance of the circuit, in ohms. Hence, as 
the current strength is directly proportional to the electromotive force, if the electro- 
motive force be increased the current strength is increased; if the electromotive force 
be decreased, the current strength is decreased. 

The current strength being inversely proportional to the resistance, if the resist- 
ance be increased the current strength is decreased ; if the resistance be decreased the 
current strength is increased. 

Ohm's law is symbolically expressed thus : — 

E 

where c represents current strength in amperes, e the electi-omotive force in volts, 
and E the resistance in ohms. 

For example, assuming a circuit of lo ohms resistance, lo volts electromotive 
force, the current strength will be one ampere, for i§ = i. 

Further, since the current strength is equal to thequotientof the electromotive force 
divided by the resistance, it is evident that the resist-ance multiplied by the current 
strength will give the electromotive force. Hence, if the current strength or, as it is 
sometimes termed, the amperage, and the resistance of a circuit be known, the electro- 
motive force will be represented by the formula e = cXk. 

Again, if c X R, be equal to e, then r must be equal to the quotient of e divided 

by c, or R = — 

*^ c. 

Consequently, when any two of the three factors concerned in Ohm's law 
are known, the third may readily be found. 

Thus, suj^pose it is desired to know the strength of current on a " circuit " between 
any two points, say, 250 miles apart, the resistance of the wire being 10 ohms, per 
mile, the resistance of the relays, say, 1,000 ohms, and the electromotive force at each 
end 50 volts. 

The total resistance of the circuit will be 3,500 ohms; the total e. m. f. 100 
Tolts, which, dividing the latter by the former, gives, ■^%, or 3V of an ampere; that 
is, approximately, yffo- of an ampere. 

As in telegraphy the current strength rarely amounts to one ampere, the term 
milliampere, which is the one thousandth of an ampere, is frequently used. Thus the 
strength of current on a circuit such as that just referred to would be equal to 29 milli- 
amperes. 

Again, if, as in practice is the case at times, it is desired to learn the electromotive 
force necessary to obtain a current strength of 29 milliamperes on a circuit of, say, 
3,500 ohms, the required information may be calculated thus: £ = .029X3,500 
equal, in round numbers, to 100 volts. 

DERIVATION OF ELECTRICAL UNITS OF MEASUREMENT. 

The practical units of electrical measurement unlike, for instance, the pound for 
weight or pressure, and foot or yard for length, are not arbitrary, or, as it were, haphazard 
units, but are derived from certain, so called, absolute electrical units, which, in turn, are 



DERIVATION OF ELECTRICAL UNITS, 



based on certain fundamental units of length, mass and time; to which, brief and 
general reference will here be made. 

The fundamental units referred to are the centimetre for length ; the gramtneiox mass, 
that is, weight ; and the second for time. 

The centimetre is the one hundredth of a metre. The inetre (equal to 39.37 inches) 
is the one ten millionth of an earth quadrant,estimated from the equator along a meridian 
to the pole. The gj-amme is equal to the weight of a cubic centimetre of water at its point 
of greatest density, namely, at 39. 2'^ f. The second is equal to the time taken by a 
pendulum, beating at the rate of 86,400 beats per day, to make one beat. 

The unit of force is termed the dyne. The dyne is equal to that force which is re- 
quired to communicate a velocity of one centimetre, per second, to one gramme mass after 
acting upon it for a period of one second. 

It may be here interpolated, although the subject will be referred to more at length 



FIG, 




elsewhere, [see Chapter III,) that, when a current exists in a wire the neighbor- 
hood of that wire becomes magnetic, and the strength of the magnetism thus developed 
depends upon and varies with the strength of current in the wire. The magnetism thus 



8 AMERICAN TELEGRAPHY. 

manifested attracts or repels ordinary magnets in the same way that like or unlike poles 
of magnets attract or repel each other. 

A magnetic pole of unit strength is one such that when it is placed at a distance of 
one centimetre from another magnetic pole of unit strength and of opposite polarity, it 
attracts the other with a force of one dyne. 

It is then said that the absolute unit of electromotive force exists in one centimetre 
portion of a circular conductor whose diameter is two centimetres, when it drives through 
that portion of the conductor a current of sufficient strength to develop at that portion a 
magnetic pole of sufficient strength to attract, with a force of one dyne, a, magnetic 
pole of unit str:ngth placed at the centre of the circle, namely, at a distance of one centi- 
metre. 

This is illustrated, theoretically, in Fig. i .* in which n may be assumed to be a unit 
magnetic pole suspended in the centre of a curved wire of one centimetre radius, cc, in 
the tray t, may represent a /essel which in the figure is purposely drawn to correspond in 
dimensions, as accurately as may be, to one cubic centimetre. Ttiis vessel may be as- 
sumed to contain enough water, of the required density, to correspond in weight to the 
unit of mass, namely, one gramme. «| 

The current so developed will be of absolute unit strength, and the resistance of the 
portion of the conductor between which this absolute unit difference of potential exists 
will represent absolute unit resistance. 

As the absolute units of electromotive force and resistance are too small for ordinary 
purposes, the units of electromotive force and resistance previously referred tqi, namely, 
the volt and the ohm, have been chosen as practical units. On the contrary, the absolute 
unit of current strength is rather large for ordinary work and, consequently, a unit of less 
value, the ampere, has been chosen for practical measurements of current strength. 

The value of the practical unit of electromotive force, the volt, is 100,000,000 
times greater than that of the absolute unit ; that of the practical unit of resistance, the 
ohm, is 1000000,000 times greater than the absolute unit of resistance, while the 
value of the practical unit of current stren^'h is one-tenth that of the absolute unit. 

The absolute units of electrical measurement : re frequently designated, the c. G. s. 
units, from the initials of the fundamental or standard units of length, time and mass, to 
which they are related. 

UXIT OF ELECTRICAL EXEKGY, 

The practical unit of electrical energy is the watt; this is the product of the 

E. M. F. by the current, or w = e x c. 746 watts are equal to one mechanical 

horse-i^ower. One mechanical horse-power is equal to the work done in I'aising 

33,000 pounds one foot in one minute. The electrical horse-power is the kilowatt, 

or 1000 watts. T'he electrical horse-power of a dynamo machine having an output 

of 25 amjieres at 200 volts is 5 kilowatts. An electric motor taking 25 am})eres at 

Sooo 
200 volts should develop) 5 kilowatts, or ^—— = 6. 7 mechanical horse-power, less 

the loss in the motor, or, if the efficiency of the motor is say 80 per cent., 5.36 
mechanical horse-powder. 

■^Suggested by figuie4o, Flemings " Lectures to Electrical Artizans." 



CHAPTER 11. 
PRIMARY BATTERIES. 

In electrical telegraphy the electromotive force required is furnished chiefly 
but not exclusively, by primary, or chemical batteries.* 

A simple voltaic cell may consist of a plate of copper and a plate of zinc placed 
in a suitable vessel containing a dilute solution of sulphuric acid. A number of such 
cells connected together is termed a battery. 

Batteries such as the well known "gravity" or the Leclanche, are generally 
designated "voltaic" or "primary" batteries— sometimes "chemical" batteries. 

A reference here to some of the chemical terms used in connection with the sub- 
ject of primary cells may assist in the subsequent descriptions. 

An atom is assumed to be an indivisible particle of a substance. A mole- 
cule is a combination or union of two or more atoms. For example, water is 
formed of molecules, each containing i atom of oxygen and 2 atoms of hydrogen, re- 
presented by the symbol HoO. An "oxide" is, generally speaking, a combina- 
tion of oxygen and some metal, for example, the oxide of zinc, which is a chemical 
combination of oxygen and zinc. The term peroxide is used to denote those 
oxides containing the highest number of oxygen atoms that will combine with a given 
metal, as, for instance, in the case of peroxide of manganese. "Chlorides," "per- 
chlorides," etc , are combinations of chlorine and other substances, as chloride of 
ammonium, commonly known as sal-ammoniac, which is a combination of 4 
l)arts hydrogen, i part nitrogen, and i part chlorine. An "acid" is, generally 
speaking, a combination of oxygen, hydrogen, and some non-metal. For instance, 
sulphuric acid is a combination of oxygen, hydrogen, and sulphur. Metals replace 
the hydrogen atoms of acids to form " salts," which are generally designated by the 
affix " ate," as, for instance, sulphate of copper, which is a chemical combination of 
sulphur, oxygen and copp>er; or sulphate of zinc, a combination of sulphur, oxygen 
and zinc. 

It is known that when a metal plate is partly immersed in a liquid, for instance 
dilute sulphuric acid, it becomes electrified. The extent and nature of this electri- 
fication varies in different metals, some metals being more highly electrified than 
others. This result is attributed to an electro-chemical difference existing between 
the different substances. P^or example, zinc is said to be electro-positive to 
copper; that is, its electric state is higher than that of copper. Thus, when 
those elements are arranged as, for instance, in a " gravity" cell, the dift'eronee of 
potential between the plates is found to be about 1.079 volts. 

That plate in such a cell which possesses the higher electric potential is 
termed the " positive " plate; that which is at the lower potential, tlie '' negative " 
plate. 

* This statement is not quite exact to-day; dynamo machines and storage batteries having supphmteii primary Iwttericd 
in a large number of the main offices of this country. 



lO AMERICAN TELEGRAPHY. 

When two such plates are connected by a wire a current is assumed to flow from 
the positive plate to the negative plate within the cell, and from the negative to the 
positive outside of the cell; the terminal of the positive plate of a cell is termed the ne- 
gative " pole; " that of the negative plate the positive pole. Thus, in the " gravity " 
cell the positive pole is at the copper plate; the negative pole at the ziuc plate. 

The current will flow so long as the difference of potential is maintained. This 
difference is maintained in the voltaic cell at the expense of the positive plate, which 
is found to be dissolved more or less rapidly, depending upon the rate at which 
" current " is supplied. In other words, the cell may be said to give out electrical 
energy at the expense of the positive plate of the cell in a manner analogous to that in 
which a steam engine gives out mechanical energy at the expense of the fuel in the 
furnace. 

Certain primary cells, when "short-circuited,"* as when the plates are connected 
outside the cell by a thick wire, or when placed in a circuit of moderately low 
resistance, for any length of time, are known to lose their effect quickly, which is 
made apparent by the rapid decrease of strength of current in the circuit. For in- 
stance, if a plate of zinc be placed with a plate of copper in a cup containing a dilute 
solution of sulphuric acid, it will be found, as has been stated, that a current will flow 
when the two plates are connected by a wire, but that, after a very short time 
the strength decreases. 

Such cells are commonly termed "open" circuit cells. This term dis- 
tinguishes them from such cells as the "gravity," which will maintain a current 
of almost uniform strength for a long period on a circuit of low resistance. Batteries, 
or cells of the latter class, are, consequently, called "constant" cells, or batteries. 

POLARIZATION. — The cause of the rapid fall in the strength of current in "open'^ 
circuit batteries, is chiefly attributable to an action within the cell which is term- 
ed />o/ariza/io?i. 

This term, polarization, in this relation, may be taken to signify a counter-elec- 
tromotive force that is set up in the cell; that is, a force tending to oppose the origi- 
nal electromotive force of the cell. The cause of polarization may be explained as 
follows : 

The difference of electro-chemical potential between some of the metals, and some 
of the metals and gases is very slight. For example, the electro-chemical difference 
between zinc and hydrogen is very small; sometimes the hydrogen is found to be 
electro-positive to the zinc. When an electric current passes through the solution 
or " electrolyte," as it is also termed, of a cell, a chemical decomposition and re- 
combination of the components of the solution takes place. Thus, in the case of a 
simple voltaic cell whose zinc and copper elements are placed in a solution of 
dilute sulphuric acid, it is assumed that the oxygen of the solution combines with 
the zinc, forming oxide of zinc, which, uniting with the sulphuric acid of the solu- 
tion, forms sulphate of zinc, setting free hydrogen, which is deposited on the cop- 
per or negative plate. 

The effect of this deposition of hydrogen on the negative, or copper, plate is to 
oppose to the zinc plate an element having an electro-chemical state or level nearly 
equal to its own, the consequence of which is that when sufticient hydrogen has ac- 



POLARIZATION. II 

cumulated on the copper plate, practically, no current flows in or from the cell. 
When this has occurred the cell is said to \yQ polarized. 

Tliat the falling off in the current is due chiefly to this cause, namely, the 
accumulation of hydrogen on the negative plate, may be shown by removing the 
hvdroo-en bubbles which have gathered on t\ie negative plate, by means of a brush, 
or bv shaking that plate in the cell, when the current will be found to increase tem- 
porarily. Or, it may be further shown by removing the zinc plate from the solution, 
after the cell has ceased to act, and substituting, therefor, another copper plate. On 
joining the two copper plates together, it will be found that a current flows from the 
hydrogen-coated copper plate to the other one until the hydrogen has been dissi- 
pated, and this current will be opposite in direction to the former current, indicating 
that it was to this counter-electromotive force that the former inaction of the cell 
was due. 

To prevent the hydrogen from accumulating on the negative plate of a cell, 
thereby to prevent polarization, many plans have been devised. When polarization 
is entirely prevented, " constant " cells are the result; when the deposit of hydrogen 
on the negative plate is only partially prevented, the cells are liable to be completely 
polarized if " short-circuited " for a time. 

In many " open " circuit cells, however, substances are employed in connection 
with or adjacent to the negative plate which tend to absorb the hydrogen as it is set 
free during the operation of the cell, and that, while the battery is inactive or open, 
coniinue to absorb, or combine with, the hydrogen on the negative plate, so that after 
such cells have rested for a time they become entirely depolarized; the substances used 
for that purpose being termed depolarizing agents. Instances of depolarizing agents 
will be given subsequently. The manner in which polarization is prevented in " con- 
stant" cells will be referred to in the course of the description of the gravity and 
other cells. 

THE GRAVITY OR CALLAUD CELL. 

The elements of the gravity cell are a copper and a zinc plate. The solution in 
which the copper plate is placed is, primarily, that formed by the dissolving of 
" Muestone " in water. Bluestone is known In chemistry as sulphate of copper. 
The zinc^ilate is immersed in water, but a solution of sulphate of zinc is, subsequently, 
formed around it. 

In the Daniell cell, which was the first constant cell invented, and of which the 
gravity, or Callaud cell, is a modification, the copper plate is placed in a cell in a solu- 
tion of sulphate of copper. In the same cell is placed a porous cup containing a dilute 
solution of sulphuric acid in which the zinc plate is immersed. 

The chemical action assumed to take place in the Daniell cell when the cir- 
cuit is closed may, in general, be stated as follows : oxygen attacks the zinc element, 
forming oxide of zinc which displaces the hydrogen of the sulphuric acid, forming sul- 
phate of zinc; the hydrogen thus released attacks a molecule of the copper sulphate, 
displacing the copper of the sulphate, and forming with the suli)hur and oxygen of 
the sulphate, sulphuric acid, which unites with a newly formed oxide of zinc, forming 
another molecule of sulphate of zinc and again releasing hydrogen which in turn dis- 
places metallic copper, as before. This action, or an equivalent one, is supposed to take 



12 



AMERICAN TELEGRAPHY. 




place throughout the cell, or until the copper plate is reached, the result being that 

the hydrogen is not set free, but, instead, an atom of pure copper is deposited on the 

copper plate of the cell. 

The chemical action that occurs in the gravity cell 

on closed circuit may be considered the same as that of 

the Daniell cell. Consequently, the elements of the cell 

remain as at first, copper and zinc, and a practically 

uniform, or constant electromotive force is thus 

maintained. In other words, since the hydrogen is di- 
verted from the copper plate, polarization does not ensue. 
The gravity battery is usually set up in glass cells 

about 6 inches in diameter by 8 inches in height. The 

copper plate is placed in the bottom of the cell; the 

zinc plate is suspended by a hanger from the rim of the 

cell, as seen in Fig. 2. An insulated copper wire is con- 
nected to the copper plate as shown. gravity cell, 

The form of zinc plate shown in the figure is called the " crowfoot." This form 

of zinc, due to d'Infreville, is in extensive use in this country in gravity batteries. 

Occasionally, star-shaped zincs, which are suspended by a " tripod " resting on the 

top of the cell, are employed. 

The bluestone, in crystals, is placed in the bottom of the cell, around the copper 
plate, and sufiicient water is poured into the cell to cover the zinc. The bluestone 
dissolves quite rapidly, forming a solution of sulj^hate of copper. 

After the cell has been in use for a short time a certain amount of sulphate of 
zinc is formed. This is also dissolved in the water of the cell, but, owing to the re- 
spective specific gravities of the two solutions, they do not sjjeedily mix; the sulphate 
of copper, being the heavier of the two solutions, remaining at the bottom. Hence the 
name of the cell. 

While, however, as just stated, the specific gravities of the respective solutions keep 
the copper sulphate below the zinc sulphate, the solutions will eventually mingle un- 
less the action of the cell is sufficient to use up the sulphate of copper as si^eedily as it 
is dissolved. When this is not the case the copper sulphate solution diffuses 
through the cell and is decomposed by the zinc plate; the oxygen joining with the 
zinc to form oxide of zinc, and the copper of the sulphate being deposited on the zinc as 
a black mud, in appearance. From what has been said it is obvious that this action, 
will, take place most rapidly when the cells are continuously idle, that is, open. 



THE CARE OF GRAVITY BATTERIES. 

The amount of bluestone to be placed in the cell depends somewhat on the work 
required of the battery. For "local" batteries, in which the sulphate of copper is rapidly 
consumed, about 3 pounds, per cell, are usually alloted. When this has been ex- 
hausted it may be assumed the cell requires cleansing. The bluestone crystals should 
be of such size as to pass through a sieve i J inch mesh, and should not be so small 
as to pass through a -^^ inch mesh. 

For ''quadruplex" circuits the "long" end of the battery need not be supplied with 



GRAVITY BATTERY. 1 3 

quite as much bluestone as the "short" end, since the former is not worked so continu- 
ously as the latter. 

In some cases it is customary to put in a small supply of bluestone when the cell 
is set up and to renew the supply as required. This plan may prove satisfactory 
where very few cells are concerned, but in a battery room containing a large number 
of cells it will not answer, unless the staff of attendants is unusually large, too much 
time being required in the operation of replenishing. Another objection to this plan 
IS that it appears to cause " caking " at the bottom of the cell. 

The condition of a cell may generally be known by its appearance. In a cell in 
good order the solution is a bright blue color, the blue changing to water color before 
reaching the zinc. A very pale or a dirty brown-colored solution is indicative of a 
deteriorated condition of the cell. The average life of a local gravity battery is 
iTO.i 4 to 6 weeks. That of a main line battery, out of which 3 or more wires are 
supplied, about 8 weeks, and a quadruplex battery from 5 to 8 months. 

HYDROMETER. — A hydromctcr is often recommended as a useful adjunct to a battery 
room, and it certainly is convenient to have one on hand when required. 

The function of the hydrometer, as its name suggests, is to indicate the density, 
that is, the specific gravity of the solution of tlie cell. Knowing the point of density 
of the solution at which the cell gives the best working results, the information fur- 
nished by the hydrometer can be availed of to keep the cell at the proper density 
point. But, again, these measurements require the attendant's time, and would not, 
on that account, work altogether satisfactorily on a large scale. For general pur- 
poses, as already said, the appearance of a battery will indicate to an intelligent at- 
tendant the time for renewal. The tendency of the battery solution is, of course, to 
become more dense, and when it is desired to withdraw some of the solution to re- 
place it with water, a syringe such as shown in Fig. 3, may be employed. 

FIG, 3 




BATTERY SYRINGE. 

The hydrometer commonly used for the foregoing purpose, consists of a glass 
bulb, about an inch in diameter, to which is attached a narrow glass stem, 5 or 6 
inches in length. A quantity of small sliot is inserted in the bulb — sufficient to sink 
it to a desired depth in pure water. A scale, somewhat similar to that of the ordinary 



14 AMERICAN TELEGRAPHY. 

thermometer, is arranged on the stem. The scale is divided into 40 or 50 sections 
or degrees; zero being placed at that portion of the stem which is level with the sur- 
face of the water. As the density of the liquid is increased, the bulb and with it the 
stem rises; the density being indicated in degrees on the scale. An indicated density 
of 30'' to 35° on certain forms of battery hydrometers has been found to be about 
the maximum consistent with the satisfactory operation of the cell. 

THE USE OF OIL ON GRAVITY BATTERIES. — The Utility of the usc of oil ou gi'avity 
batteries is questioned every now and again. This use of oil refers to the placing 
of a layer of oil on the liquid to prevent evaporation, etc. The objections generally 
offered to its use are that it makes the cell and the plates more difficult to clean ; 
it cakes and falls to the bottom; it corrodes the insulation of the copper connecting- 
wire; it does not prevent gathering of white salts on cell; it is dangerous as condu- 
cive to fires, etc. 

The answer to these objections is that with proper precautions they need not be 
valid. 

The cell in which oil has been used, and also the plates, are readily freed of any oil 
that may adhere to them, by the application of moistened waste, dipped in sand. Battery 
oil of the proper quality does not cake or flake. Ordinary oil is, it is known, a solvent 
of rubber compounds, and, but to a less extent, of gutta-percha, and when these sub- 
stances are used as the insulating material of the copper connecting wires, they are 
soon softened, especially if the oil employed has even a trace of naphtha. But a com-, 
pound composed of gutta-percha and paraffin withstands the oil very well. Good oil 
certainly does prevent evaporation of the water of the solution, and the gathering of 
"white salts" on the jar. This has been proved repeatedly. When the salts have 
started to " climb " before the oil has been applied, they will continue to do so, but to 
a more limited extent. The oil should be applied when the cell is newly set up. 

The advantages of the use of oil arise from the fact that, preventing evaporation 
of the liquid and the formation of "creeping" or "white salts," a much more efficient 
battery is secured with a much smaller force of attendants than would otherwise be 
required. These white salts, or evaporated sulphate of zinc, when oil is not used, rap- 
idly creep over the edge of the cell and down to the battery stand. This dry sulphate 
of zinc is a good conductor of electricity, and as it spreads from cell to cell is most 
liable to short-circuit them, in whole or in part; thereby, of course, wasting the 
battery. 

By preventing evaporation the solution is kept constantly above the zinc, where- 
as, when oil is not used it is a common thing to find the battery oj^en, due to the solu- 
tion having fallen below the zinc. In one battery room of 5,000 cells, within the writer's 
knowledge, where oil was not used, one attendant was kept busy one day and a half 
to two days in the week replenishing the cells with water, and even this amount of 
attention did not suffice to obviate all trouble due to opening of batteries from the 
aforesaid cause. 

As intimated, a good quality of oil should be used for this purpose. It should 
have the following requisites : — a color readily distinguishable from the solution, for 
instance, an auburn tint; should spread over the surface of solution readily, otherwise 
waste of oil and of time in applying it will ensue; should be odorless, non-inflamma- 



OIL GN BATTERIES. 1 5 

ble under 400°F, and free from traces of naphtha or acid. A good lubricatmg oil, 
a product of petroleum, will meet all of these requirements. 

Battery oil may, with care, be used over and over again and, therefore, should be 
carefully preserved when the cells are being cleansed or renewed. The best method 
for thus preserving the oil at such times is to pour the solution of the cells, oil includ- 
ed, into a barrel having a faucet at the bottom. The oil will float on the surface of 
the solution. AVhen the barrel is full the solution is drawn off at the faucet until the 
oil is reached, when the latter is run into a separate vessel. 

The evaporation of the solution and the formation of salts may be prevented by 
providing the cells with covers nearly air tight, but this is a diflicult thing to do 
and to maintain on a large scale. In the hasty search for trouble in cells the 
cover will be removed and not put back, witli the result that evaporation, etc., 
will go on. But when this plan can be properly carried out, as it may be in small 
battery rooms, it is a good and efficient one. 

A method frequently employed to prevent climbing salts is to smear the upper 
edge of the cells with paraffin. Still another is to place a strip of oiled cloth around 
the upper, inside edge of the cell. 

In a few more years it is quite possible that dynamo-electric machines will have 
so far replaced chemical batteries that the use of oil or any other preventive of evap- 
oration, climbing salts, etc., will not be of so much importance. But as hundreds of 
thousands of gravity cells are at present in service in this country the question of 
improvement in their maintenance is still one of great interest. 

GENERAL xoTES ON" GRAVITY BATTERIES. — In Setting up battcrics, old solution from 
an exhausted battery is sometimes employed. This puts the battery in a working con- 
dition at once, ?.s it reduces the internal resistance of the battery to nearly the normal 
point; sulphate of zinc being, as stated, a good conductor. At other times the battery 
is put on short circuit for twenty-four to forty-eight hours. This also brings the in- 
ternal resistance down to a working basis, but at a loss of considerable material, since 
the reduced internal resistance is due to the presence of zinc sulphate in the solution, 
and this has been formed by the decomposition of a part of the zinc element as well 
as a part of the sulphate of copper of the solution. It has been the writer's experi- 
ence, however, that much less black copper attaches to the zinc when the cells are 
short-circuited at starting, than when the old solution is used.* 

The in /em a/ remstanGe of a battery may be explained thus: While a voltaic 

cell is a "source" of electromotive force, its elements, the plates, solution, etc., are con- 
ductors and, consequently, like other conductors, possess resistance. In a gravity cell 
this resistance is from 2 to 3 ohms, depending on the size of the plates, their 
nearness to each other, the nature of the solution, etc. This resistance is called the 
/;//^r/z<:z/ resistance of the cell, in contradistinction to the resistance of the rest of the 
circuit which is termed the ^.T/^r;?^/ resistance. The internal and external resistances 
of the circuit comprise the total resistance of the circuit. 

Much difficulty, delay, and loss, is frequently occasioned by the breaking of 
glass cells, apparently spontaneously, after they have been set up. The writer has 
known as higli a breakage as 18^ of the glass cells in use in an office in one month. 

* All aiiHly8is of zinc scale from gravity battery, by Dr. C. M. Cresseii, showed 45.06 parts of zinc, 2.98 of copper. M *.f 
lead, 1.87 of iron. 



i6 



AMERICAN TELEGRAPHY 



Tliese breakages were traced to changes in temperature of the battery room. 
The remedy for this is an improved grade of ceU. One that is better annealed. 

It has been found of advantage to connect the copper connecting wire to the cop- 
]^er plate at a point near the bottom of the cell, and to bring the insulated covering 
of the wire close to that point. 

The beaten copper and the scrapings from the zincs should be carefully gathered, 
as they may be sold at a figure considerably above the expense of handling. 

Care should be taken in cold weather to maintain the temperature of the gravi- 
ty battery above 65° or 70°F, for below that temperature the internal resistance of 
cells increases very rapidly, so much so that even at 5o°F. the battery becomes 
much impaired. 

It may be remarked here that the resistance of liquids decreases as the tempera- 
ture rises. 

A number of modifications of the Callaud cell have been designed, mainly, to pre- 
vent accumulations of black copper on the zinc. They differ from the ordinary gravity 
cell, chiefly in the manner of supporting or enclosing the zinc element. In some a 
porous cup with a flange, or rim, on its upper edge, which rests on the top of the 
glass jar, is employed and the zinc is placed in this cup with a few ounces of mer- 
cury, the latter for amalgamating purposes. In other respects the elements used are 
the same as those of the gravity battery, namely sulphate of copper and metallic 
copper. In other modifications such as that due to Mr. Delaney the zinc is enclosed 
in a cloth bag. 

THE LECLANCHE CELL. 

There are many modifications of the Leclanche cell. One form is shown in Fig. 4. 

In this cell polarization is not altogether prevented , 
but it is measurably so. The depolarizing agent em- 
ployed is peroxide of manganese, which is placed 
around the carbon element. 

The plates of the Leclanche cell. Fig. 4, are zinc 
and carbon. The positive or zhic element generally 
consists of a rod z of that metal about half an inch 
thick, placed in a solution of sal-ammoniac contained 
in a glass cell c. The negative element of the cell 
consists of a rod or plate of carbon k. This rod is 
placed in a porous cup p within the glass cell. The 
porous cup is filled with a mixture of small lumps of 
carbon and granulated peroxide of manganese. The 
porous cup permits the liquid to pass through and 
moisten the manganese and carbon. 

LECLANCHE CELL. 

Chloride of Ammonium, commonly known as sal-ammoniac, is a combination of 
chlorine and ammonia (ammonia being a compound of hydrogen and nitrogen); the 
molecule consisting, as previously intimated, of, hydrogen, 4 atoms; nilrogvii, i 
atom; chlorine, i atom. In tiie action which is assumed to accompaLy 



FIG. 4. 




THE LECLANCHE CELL. I 7 

the passage of the current the chloride of ammonium is decomposed, the chlorine leaving 
the ammonia and hydrogen to unite with an atom of the zinc plate, forming chloride 
of zinc, and setting free ammonia and hydrogen. The ammonia is dissolved in the 
water of the cell ; the hydrogen enters the porous cup and would very speedily polar- 
ize the cell by adhering to the carbon plate, thereby setting up a counter- electromotiye 
force, but that it encounters the peroxide of manganese, which readily yields up a part 
of its oxygen, forming by the combination Ho O, that is, water ; leaving what is 
termed a sesqui-oxide of manganese. This absorption or combination of the hydrogen 
prevents immediate polarization, but, apparently, hydrogen is evolved during the oper- 
ation of the cell more rapidly than it can combine with the oxygen of the mangan. 
ese, inasmuch as it is found that polarization soon takes place when the cell is short- 
circuited. When, however, it is left open for a time depolarization ensues and 
the cell recuperates; in a short time attaining its normal electromotive force. 

An advantage of the combination of carbon granulations with the carbon plate is 
that it practically increases the surface of the negative element, and thus tends to increase* 
the constancy of the cell, since, in addition to the counter-electromotive force set up by 
the hydrogen its presence on the surface of the carbon increases the internal resistance of 
the cell by reducing its conducting surface. 

The Leclanche cell is extensively used in telephony, district messenger service, 
etc., etc., and in connection with other systems where open circuit batteries are avail- 
able. Its electromotive force is 1.47 volts. Its internal resistance varies with the size of 
the elements and their distance from each other, but it is generally less than i ohm. 

The contact with the carbon is generally made by drilling holes in the ends of the 
plate, into which lead is cast, and into which, at the same time, a brass contact screw 
is also inserted. The upper end of the carbon rod is thoroughly soaked in paraffin 
wax to prevent the rising of salts from the cell, but, notwithstanding this, the binding 
screw is frequently corroded by the action of the salts, after a few months use, and, as a 
consequence, the cell is rendered useless until a firm contact is re-established between 
the carbon plate and binding screw. 

In setting up the Leclanche cell an excess of sal-ammoniac should not be used, as a 
saturated solution tends to a deposit of .crystals on the zinc. On the other hand, the 
solution should not be allowed to become too weak, as in that case chloride of zinc will 
form on the zinc. Both of which causes materially increase the resistance of the cell. 
Some sal-ammoniac should be added to the cell from time to time depending upon 
the extent of its use. 

The Leclanche cell has the advantage over the " gravity " and many other cells that 
when not in actual use, there is no waste of the materials of the cell. 

THE FULLER CELL. 

This cell is frequently employed in telegraphy where a strong current is re- 
quired. It is in extensive use as a source of electromotive force for telegrapli lines in 
Great Britain, taking there the place of the gravity cell in this country.* 

The plates used in the Fuller cell are zinc and carbon. The zinc plate z. Fig. 5, 
is pyramidal, or cone shaped, and is placed within a porous cup c containing a dilute 
solution of sulphuric acid. The carbon plate k is placed outside of the porous cup, but 

* This cell is now used very largely iu telephony, in this country, as the transmitter battery. 



i8 



AMERICAN TiiLEGRAPHY. 



FIG. 




FULLER CELL. 



within the gbiss jar j. The carbon is partly immersed in a sohition composed of bich- 
romate of potash, 3 parts; sulphnric acid, i part, and water 9 parts. This solution is 
generally known as electropoion. In the bot- 
tom of the porous cup about two ounces of 
mercury are placed for the purpose of amal- 
gamating the zinc. The necessity for amal- 
gamating the zinc, which consists in coating 
the zinc with mercury, arises from this, that 
in commercial zinc there are more or less 
impurities such as lead, iron, tin, etc., and 
when such zinc is placed in a dilute acid, a 
local current, or local action, as it is called, 
is set up between the impure metals in the 
zinc and the zinc itself, which action wastes 
the zinc to no purpose. 

The act of coating the zinc with 
mercury appears to form on its surface 
an amalgam, or alloy, which includes also 
the iron and other impurities of the zinc, 
that brings the entire surface of the 
zinc to a uniform condition. Consequently, 

there is no tendency to inequality of electrical condition so far as that portion of the 
zinc exposed to the acid solution is concerned, and hence, practically, no local action. 
As the zinc becomes decomposed, during the 023eration of the cell, the mercury passes 
to the next particle of zinc, and thus, automatically, maintains the amalgamation. The 
impure particles of the amalgam become detached as the zinc proper dissolves from 
around them, and fall to the bottom of the cell. Ordinarilyj zinc is amalgamated by 
pouring or rubbing mercury over it, and wijjing off any surplus. This is effective 
until the mercury wears or drops off, when local action again sets in. In the Fuller 
cell, as stated, the mercury is placed in the bottom of the porous cup, and by 
capillary action the mercury climbs the zinc,, and keeps it permanently amalgamated. 
This is the chief advantage of the Fuller cell over other somewhat similar batteries. 

Bichromate of potash is a combination of oxygen and the metals chromium and 
potassium. When the circuit of the cell is completed it is assumed that the sulphuric 
acid (the supply of which passes from the outer solution into the porous cup,) attacks 
the zinc, ultimately forming sulphate of zinc and setting free hydrogen; polarization 
being prevented by the combination of the hydrogen thus set free with oxygen of 
the bichromate of potash. The electromotive force of the Fuller cell is 2.028 volts. 
Its internal resistance, about .5 ohm. The internal resistance may be decreased still 
farther by increasing the size of the carbon and zinc. When this cell is not over- 
worked it will last four or five months without attention, but otherwise it should re- 
ceive attention about once a month. Very little action takes place in this cell when 
the circuit is open. When the solution, originally orange, due to the bichromate 
crystals, acquires a bluish tint, it is evidence that additional crystals are necessary. 
Sliould the solution retain its orange color, but is, nevertheless, inoperative, fresh 



CLORIDE OF SILVER CELL. 



19 



sulphuric acid should be added. When the color of the solution is bright, and the 
battery still remains inactive, it may be assumed that it requires renewing. 

CHLOEIDE OF SILVER CELL. 



This cell is shown in Fio\ 6 



the positive element, and c, a rod of 



Its elements are z 
chloride of 

silver, the negative element. A silver wire s, is - — 

cast into the chloride of silver element. The cell 
itself is, in practice, generally, a small glass vessel v about 
two and a half inches long, by one inch wide. The " ex- 
(•iting fluid," or solution, is sal-ammoniac dissolved in water. 
After the solution has been added the vessel is closed by 
paraffin wax, which, practically, hermetically seals the cell. 

This cell is often used as a standard of electromotive 
force. Its E. M. P., is about 1.03 volts. Its internal resis- 
tance is variable, and is at first about 4 ohms, but becomes 
much higher after ordinary usage. 

Owing to its compactness and portability, a battery of 
these cells is much used in this country in measuring the in- 
sulation resistance of cables, etc. A form of this battery ex- 

FIG. 7. 



a rod of chemically pure zinc, 

FIG. 6. 



c 





■^y 



CHLORIDE OF SILVER CELL. 



tensively iTsed for this purpose, 
and known as the Barrett chlor- 
ide of silver battery, is shown 



in Fii 



The ceils are placed 



together as indicated in Fig. 8, 
in any desired number, in a 
frame, f, with compartments for 
each cell, and Avith one of the 
electrodes, or plates of eacli cell 
extending above the frame as 
shown. The entire battery is 
"■•■■•■■-^^^^^^^ then surrounded by liquid para- 

cHLORiDE OF SILVER BATTERY. ffiu wax, whicli spccdlly hard- 

ens. This well insulates the battery. The cells are joined together permanently, as 
shown in Fig. 8, but until the electrodes are connected by a wire outside of the frame 
the battery does not become active. By the use of hollow metal plugs, which fit over 
ine ends of the protruding electrodes, and to which plugs, insulated wires are attached, 
as shown in Fig. 7, any part or all of the cells may be brought into circuit. For in- 



stance, the cells in Fio;. 8, 



between and including i 



and 6, are 



in circuit. 



A poh 



20 



AMERICAN TELEGRAPHY. 



changing switch is placed on the cover of the box at x? ^J means of which the polarity 
of the battery may be reversed at will. This pole reverser is shown in Fig. 7. 




A battery of one hundred chloride of silver cells can be readily placed within a 
box one foot square. 

THE EDISON-LALANDE CELL. 

This cell, which is a modification, chiefly as to mechanical construction, of the " De 
Lalande and Chaperon" cell, is illustrated in Fig. 9. Its elements are a zinc plate z 
and a block of copper oxide c, upheld by a frame/. The solu- 
tion of the cell is oxide of potassium, or caustic potash, dis- 
solved in water. The plates are suspended from the cover of 
the cell as shown. 

Polarization is prevented by the '^decomposition of the 
water of the solution, the oxygen of the water combining with 
the zinc to form oxide of zinc, which in turn combines with the- 
potash to form an exceedingly soluble double salt of zinc and 
potash." The hydrogen liberated from the water combine^^ 
with the oxygen of the copper oxide, re-forming water and de- 
positing pure, metallic copper. 

The coi^per oxide of the " Edison-Lalande " cell is ch- 
ained by roasting copper turnings which are then ground finely 
and afterwards formed into blocks of suitable size. 

To prevent evaporation and the formation of creeping salts, 
a layer of suitable oil is placed over the liquid. This,. it is said, also prevents a com- 
bination of di- oxide of carbon from the air with the potassium of the solution. 




EDISON DELANDE CELL. 



THE EDISON-LALANDE CELL. 2 1 

The electromotive force of the cell is low, being at first about .98 volt, and after 
■working for a short time it falls to .7 or .75 volt. The internal resistance of the cell 
is very low and varies with the size of the cell; the resistance of the largest cell being 
but .025: tliat is xjfu ohm- The internal resistance decreases after the cell has been in oper- 
ation for a few hours, owing to the substitution of the reduced metallic copper for the 
copper oxide; the former being a better conductor than the oxide. In the "Edison- 
Lalande '' cell a film of metallic copper is deposited, in advance, on the copper oxide, 
thereby procuring a minimum internal resistance immediately the cell is connected in 
circuit. The manufacturers advise that, in setting up the cell, one-half the caustic potash 
sticks, which accompany the cell, should first be placed in the jar, after which the jar 
should be filled to within one inch from the top with water. The liquid should be 
stirred occasionally or until the caustic potash is dissolved, when the balance of the 
caustic may be added, tlie liquid being then stirred as before. This precaution is 
rendered necessary by the increase of temperature that accompanies the solution of the 
caustic potash. This solution is harmful to the skin. The hands should therefore 
be carefnlly guarded against direct contact with it. 

It may be added that the Edison-Lalande cell is well adapted to purposes re- 
quiring strong currents. A cell of this kind having an e, m. p. of .75 volt and an internal 
resistance of .025 ohm would, on short-circuit, furnish a current of 30 amperes. A 
gravity cell having i volt e. m. f. and 2 ohms internal resistance would furnish a 
•current of but .5 ampere under similar conditions. 



DRY BATTERIES. 

A form of zinc-carbon primary cell, known as a "dry," but which is more 
correctly a moist battery, is one in which the usual liquid solutions are dispensed with, 
and instead the cell is partly filled with substances which are capable of retaining 
moisture for a considerable time ; or to which a small amount of liquid may be ad- 
ded from time to time. These substances hold the "exciting agents," such as sal-am- 
moniac, in solution. The freedom of these cells from climbing salts, accidental spill- 
ing of the solution, etc., has rendered them very desirable for use in telephony; call 
bell service, etc., and the demand for them has grown rapidly in recent years, with 
the result that there is now a large variety of such cells in the market. 

Some forms of dry batteries, like the Leclanche liquid cell, have the advantage 
that they do not become inoperative at low temperatures, as do> for instance, the 
Daniel and " gravity " liquid batteries. Certain dry batteries have been found to per- 
form satisfactory service when exposed to temperatures ranging considerably below 
zero,Fahrenheit. 



22 



AMERICAN TELEGRAPHY. 



THE BUENLEY DRY CELL. 

One form of dry cell, known as the Burnley, is shown in Fig. lo, in eross- 
section. 

In this cell the usual glass jar is replaced by a zinc tube, or cup a to which a 
clamping screw b, is rigidly attached. c is a solid carbon cylinder, forming the 
negative plate of the cell. It is provided with a connecting screw d. The zinc cup 

is lined with an exciting agent, e, whicli, 
practically, corresponds to the solution cf 
7^ inmnni ^MJ IIII in ii ^^ Leclanche cell, and is composed of sal-am- 

moniac, I part ; chloride of zinc, i part ; plaster, 
3 parts; .87 parts of flour, and 2 parts of water. 

In constructing this cell, the ingredients of 
the exciting agent are mixed together, forming a 
semi-liquid, which is poured into the cup a 
around a plunger that has been temporarily in- 
serted in the centre of the cup, when the mass 
A \ l^^llllllllllMlitHIIII^^ speedily stiffens. The plunger is then removed 

•/i^' ri^SrlllllllilRllMllllllllllS'H^ and the carbon rod is inserted in its place. The 

"jp carbon, however, does not occupy all of the 
space left by the plunger, and the space around 
the carbon is filled with a semi-solid compound, 
F in the figure, -consisting of sal-ammoniac, i 
part; chloride of zinc, i part; peroxide of man- 
ganese, I part; granulated carbon, i part; plas- 
ter, 3 parts, I part of flour and 2 parts of water. 
After the ingredients are placed in the cell, 
it is sealed with bitumen, g, or any equivalent 
substance. 

The main constructional feature of this dry 

battery is the manner in whicli the layers of the 

exciting and depolarizing agents are arranged 

within and around the zinc and carbon plates, respectively. The depolarizing 

agent in this cell, it will be. noted, is also practically similar to that of the Leclancne, 

This cell has an e. m. f. of 1.4 volt, and an internal resistance of i ohm. It 

gives a practically constant current during the life of the cell. 

the gassner dry cell. 
In Fig. II is shown, in cross-section,' the Gassner dry cell. In the figure zj is a 
zinc cup, to which a clamping screw s, is firmly attached. cm is a cylinder con= 
t lined within the zinc cup, composed of carbon and manganese, to which is attached 
the binding post c. The space between the two cylinders, zj and cm, is filled with 
an exciting agent, in liquid form, which afterwards becomes comparatively solid. 
The whole is sealed in the cup by some suitable material, m. The ingredients of this 
exciting agent are compounded about as follows: i part by weight of oxide of zinc; 
I part sal-ammoniac; 3 parts of plaster; i part chloride of zinc; 2 parts water. 




THE BURNLEY DRY CELL. 



DRY BATTERIES. 



23 



The claimed effect of the oxide of zinc upon the composition is to loosen and 
make it porous, and tliat the greater porosity tlius secured facilitates the interchange of 
the gases and diminishes the tendency to polarization. The internal resistance of the 
cell is not increased by the oxide of zinc, inasmuch as the latter is a better conductor 
than the plaster of the compound. 




FIG. 12. 



ZJ 




DRY CELL. 



GASSNER DRY CELL. 



The general external appearance of a "dry" cell is illustrated in Fig. 12. The 
structure of the cell is, however, frequently varied both as to size and shape. 

Used as a'* call bell" battery, or for similar purposes, successful, dry batteries 
will last, without renewal, for from six months to two years, depending on the service 
performed. 



ARRANGEMENT OF CELLS IN BATTERIES. 

As already stated, a number of voltaic cells joined together is termed a bat- 
tery. 

Cells ijst Series. — When it is desired to obtain a greater electromotive force 
than that developed by one cell, a number of cells are connected, as in Fig. 13; the 
positive pole of tlie lirst cell being connected to the negative pole of the second 
cell; the positive of the second cell .0 the neo-ative of the third cell, and so on. 



24 



AMERICAN TELEGRAPHY. 



FIG. 13. 



Cells thus placed are said to be arranged in series. When thus arranged, the 
electromotive force of each cell is added to that of its neighbor, and the resulting 
electromotive force is equal to the sum of the electromotive forces of all the cells. 
Assuming the e. m. f. of each cell in Fig. 13 to be i volt, the total e. m. f. developed 

by the series will, consequently, be 6 
volts, and, in the figure, the direction 
of the current in the external circuit is 
assumed to be from the positive pole at 
6, to zero, as indicated by the arrows, 
that is, from the point of high to the 
point of lower potential. As each cell 
increases the electromotive force by i 
volt, the E. M. F. at any one of the cells, 
that is, the difference of potential bet- 
ween that cell and zero, will be found 
to be, practically, as indicated by the 
figures. 

Cells in Multiple. — When it is 

desired to obtain additional strength of 

current without increased electromotive 

force, the cells are connected as shown 

Fig. 14, which rei3resents two rows 




m 



CELLS IN SERIES. 



of 6 cells, each, with the negative pole 
of each row joined at a, and the positive pole of each row Joined at b. When thus 
arranged the two rows of cells are said to be in multiple, or parallel. 



FIG 14. 




CELLS IN MULTIPLE. 



DRY BATTERIES. 25 

Thus aiTaiiged, each cell of each row adds its e. m. r. to that of its adjoinins: 
cell, so that each row has at its terminals a difference of potential of 6 volts, as in the 
case of the separate row of 6 cells. Fig. 13. But, in the case of the cells in multiple, 
twice as much current will flow in the external circuit, wire w. Fig. 14, as in wire w, 
Fig. 13. A cell or battery whose terminals are thus connected by a wire of practi- 
cally no resistance, is said to be " short circuited." 

The doubling of the current in the case of Fig. 14, is due to the fact that the in- 
ternal resistance of the cells has been reduced one-half, as may be shown: 

Assuming, as before, (Fig's. 13 and 14) that each cell has an e. m. f. of i volt, 
and an internal resistance of 2 ohms; the "internal resistance" being, as already said, 
the resistance of the plates, the connecting wires in the cell and the liquid of the cell; 
which internal resistance varies inversely with the size of the plates, their nearness to 
each other, and with the nature and condition of the solution of the cell. The " ex- 
ternal *' resistance, as previously remarked, is the resistance of the circuit outside of 
the cell. 

With 6 cells in series, therefore, we have 6 volts e. m. f., and 12 ohms internal 

resistance, which, according to Ohm's law, gives ^ — = | ampere. In the case of 

Fig. 14, on the other hand, we have, by placing the cells in multiple, practically 
doubled the size of the cells and, consequently, have halved the resistance, so that, 
while the electromotive force is the same as before, the total internal resistance, that 
is the "joint" resistance of the two rows of cells, is 6 ohms, and the strength of cur- 
rent in wire w will be — = I ampere. In other words, if instead of using two rows 

6 ohms 

of cells we should reduce the internal resistance of the first row by increasing the size 

of the tiopper and zinc plates, and by bringing the plates in the cell nearer to each 

other, so that the internal resistance of each cell should be but i ohm, instead of 2 

ohms, we would have, in the external circuit, virtually, the same result as with the two 

^, ^ . 6 volts 

rows; that is, - — r = 1 ampere. 

6 ohms ^ 

If the 12 cells. Fig. 14, were placed in one series instead of in multiple, the result- 
ing electromotive force would be 12 volts, and the strength of current would be 

i2jNro ts _^ ampere. And, further, it will be found that as long as each cell has an 
24 ohms 

e. m. f. of I volt, and an internal resistance of 2 ohms and the external resistance of 

the circuit continues low, the current will be the same in the external circuit whether 

we have but i cell or 1,000 cells in series, since, in that case, it will be evident that 

for every volt electromotive force added to the circuit there are added to the same 

circuit, 2 ohms resistance. For example, with i cell, ^ — -- = | ampere, or 

'- 2 ohmj 

with 1,000 cells, L^^^^J^^ =i ampere. 
2,000 ohms 

Cells in Opposition. — In Fig. 15 is shown a set of 6 cells, 2 of which are 

placed in opposition, as regards their poles, to the other 4. This figure may be 

used to illustrate what is termed counter-electromotive force. It will be seen by 



26 



AMERICAN TELEGRAPHY. 




2 3 4 

CELLS IN OPPOSITION. 



reference to the arrangement of the posi- 
tive (-f-) and negative ( — ) signs over the ^ / " ~ ^+ 
cells, that cells i and 2 are opposed to 
cells 3, 4, 5 and 6. The effect of this is 
that the electromotive force of cells, i and 
2, offsets, or neutralizes, the electromotive ^ 
force of two of the remaining cells, and, as 
a consequence of this opposing, or counter- 
electromotive force, the available, or effec- 
tive electromotive force of the circuit is 

only equal to that of 2 cells, or 2 volts. And, since each cell in the circuit retains its 
usual internal resistance, the current flowing in the circuit of the 6 cells, when thus 
arranged, will be ^^ r= -i of an ampere, as against \ ampere when the cells were 
connected in "straight" series. 

Further, if, in Fig. 14, the wire w be severed, no current will flow in the 
cells, inasmuch as the 6 volts of row x, will oppose the 6 volts of row ji', thus present- 
ing an equal potential, or pressure^ at a and b, and thereby preventing any tendency to 
a flow of current between those points ; the flow of current, as stated elsewhere, 
depending on a difference of potential, or pressure. 

In all of the foregoing it has been assumed, as intimated, that the resistance of 
the connecting wires w, is so low as to be negligible; when, in 23ractice, this is not the 
case, the resistance of those wires must be included, in calculating, by Ohm's law, the 
resulting strength of current, instances of which will be given later. 



An improvement made recently by Mr. G. dTnfreville, in the form of the zinc of 



the gravity battery, is shown in Figs. 



15 h. '*In d'Infreville's crow-foot battery 



FIG. I5«. 




the disadvantage exists that after the "feet ' of the 
zinc have been consumed, the internal resistance 
becomes so great that a new zinc must be sup- 
plied. With the " wasteless " zinc the stub is used 
in the cell until none of it remains. Each zinc, as 
shown in Fig. 15^, is furnished with a tapered post 
which is coned out underneath ; the size of the 
socket thus formed corresponding to that of the 
tapered post. The post is forced into the socket 



ternal resistance of the cell to .7 



as indicated in Fig. 15 Z>, 
in such a manner that two 
or more zincs, or portions 
of zincs, may be in use at 
once in the cell. The 
method of hanging the 
cell is shown. The doub- 
led zinc reduces the in- 
ohm." 



FIG. 153. 




CHAPTER III. 

THE DYNAMO MACHINE IN TELEGRAPHY. 

Ten or twelve years ago it would have been unnecessary to write a chapter de- 
voted to tlie dynamo-electric machine in a book descriptive of electrical telegraphy, 
but to-day such a work would scarcely be complete without reference to that 
machine. 

The dynamo machine was first extensively used in telegraphy in this country, to 
take the place of gravity battery previously used to furnish the current required 
in the main office of the Western Union Telegraph Company in New York City, 
1880. It is now employed for a similar purpose in many other large telegraph offices 
in this country. 

It is known that not more than 3 or 4 circuits at most can be advantageously 
worked from one gravity battery. 

This is due mainly to the fact that the variation in the strength of the current 
furnished by this form of battery, when many line wires are being "fed " from one 
of them, renders signals unsteady. This variation of the current strength is due to 
a constantly changing external resistance, caused by the opening and closing of the 
wires in the act of operating them. When a source of electromotive force having a 
very low "internal" resistance is employed, the fluctuations of the external resist- 
ance do not materially affect the amount, or strength of current supplied to the vari- 
ous w4res forming the " external "resistance. 

An explanation may be useful here, of the causes which lead to this variation of 
current strength when gravity batteries are employed, and of the statement just 
made, namely, that, with a source of electromotive force having low internal resistance, 
this variation would not occur. But, as to a proper comprehension of the subject, a 
knoAvledge of the laws of the "joint " resistance of circuits, and of the distribution of 
current strength in divided circuits, is essential, reference will first be had to those 
laws before proceeding with the explanation. As those important laws are also con- 
cerned in the operation of certain systems, notably the Field key system, and in meth- 
ods of testing described herein, they will be referred to at some length. 

Joint Resistance of Circuits. — The resistance of a conductor of a given lengtlt 
decreases in proportion as its weight, or mass, is increased. Thus, if a wire i mile in 
length and weighing 200 pounds, be assumed to have a resistance of 6 ohms, per mile,, 
a wire of the same length and material, weighing 400 pounds, will have a resistance 
of 3 ohms. 

If, as in Fig. 15 ^, a number of conductors be connected with a given battery, or 
other source of e. m. f., the whole may be classed as one circuit, the total resistance 
of which will be that due to the internal resistance of the battery and the exter- 



28 



AMERICAX TELEGRAPHY. 



nal resistance of the conductor; the external resistance in this instance being the 
" joint " resistance of the 3 conductors. 



^r 




In Fig. 15 ^, let A B c represent 3 copper 
wires of equal diameter and length, weighing 
3 j^ounds each, and each having a resistance 
of 1 2 ohms. It is evident then that, as regards 
electrical resistance, these 3 wires are equal to i 
wire of similar length, weighing 9 pounds. 
Consequently, if the 3 wires be measured to- 
gether, it will be equal to measuring i wire of 
9 pounds weight, and hence, the joint resist- 
ance of the said 3 wires will be but | of 12 ohms, 
namely, 4 ohms, and, if we neglect for the pre- 
sent the resistance of the battery, the total 
resistance of the circuit will be 4 ohms. Conductors arranged as in Fig. 15 ^, are 
said to be in "multiple " or in "parallel; " and such a circuit as that shown in^the 
figure, is termed a " divided circuit." 

If the weight, length and material, and, consequently, the resistance of each con- 
ductor of a circuit were the same, it would be easy to calculate the joint resistance 
of any number of circuits arranged in multiple. For instance, the joint resistance of, 
say, 20 wires of equal weight and length, each having a resistance of 20 ohms, would 
be equal to the resistance of i wire of similar length weighing twenty times as much 
as any one of the 20 wires; that is, the resistance of such a wire would be i ohm. 
Xor, is it necessary, to arrive at this conclusion, that each of, say 20 wires, should be 
of the same weight and length. If each wire has the same resistance, the joint 
resistance of the 20 wires will be i ohm. For, evidently, electrically considered, 
a wire measuring 20 ohms, whatever be its actual weight and length, will be the 
equivalent (as to resistance) of any other wire measuring 20 ohms. Thus, an easy 
way to find the joint resistance of a number of circuits of equal resistances, in multi- 
ple, is to divide the resistance of any one of the circuits by the total number of wires, 

20 
as in the last instance : — ^ = i ohm. 
20 

But when the respective resistances of the wires placed in multiple are not alike, 
the rule for finding their joint resistance may seem more complicated. In that case 
the rule is as follows: — The joint resistance of circuits in multiple is equal to the recip7'o- 
cal of the sum of the reciprocals of the 7'espective resistances of the circuits. 

This statement is, not, however, as formidable as it may, to the novice, at first 
sight appear. Indeed, the plan previously described for finding the joint resistance of 
circuits of similar resistances, is, virtually, the result of the working out of that state- 
ment, as we shall presently see. We shall see, also, that the statement is merely the 
expression of well-known electrical laws. 

The reciprocal of any number is the quotient obtained by dividing i by that 
number. And the sum of a given amount of reciprocals is obtained by simply 
adding those quotients together. Consequently, the reciprocal of the sum of any 
amount of reciprocals may be obtained by dividing i by that sum. 



JOINT RESISTANCE. 29 

For example, the reciprocal of 20 is .05; that is ^\= .05. On the other hand, 
the reciprocal of .05 is 20 ; that is .^V = 20. Tims, the reciprocal of a number may 
be called the converse of that number. Again, the sum of reciprocals may be shown 
thus: 2L4-^ty4-^i^ which is equal to ,o5 + .o5+.o5= .15. Hence, the recipro- 
cal of the sum of the reciprocals of 20-I-20+20 must be ^^ ^ ^ that is; 

■ ■ — -= 3-1^ = 6.66 

.05 + .05+.05 

Now, electrical conductance, or conductivity, is the reciprocal, or converse, of re- 
sistance, and, contrariwise, resistance is, of course, the reciprocal, or converse, of con- 
ductance. That which tends to increase resistance decreases conductance, and what- 
ever increases conductance decreases resistance. 

There is no generally adopted unit of conductance, as yet, but Sir Wm. Thom- 
son has suggested the term mho, as such a unit. This word, it will be perceived, is 
the converse of ohm, and thus is suggestive of the converse of resistance. 

The conductance of a conductor, obviously, increases directly as its power of con- 
ducting is increased. Thus, if we join up 2 wires in multiple, each having a conduct- 
ance of , say, 6 mhos, the joint conductance of the wires would be the sum of their 
respective conductances, that is, 12 mhos. Or, if 3 wires of 6, 12 and 18 mhos, each, 
were thus connected the joint conductance would be 36 mhos. That is, the 
conductance of the 3 wires combined would be equal to the conductance of 6 wires of 
6 mhos each, or to i wire of 36 mhos conductance. For example, assuming the case 
of any 3 wires having each a resistance of 6 ohms, it is clear, from what has been 
stated, that they would each have a conductance of \ mho. 

Now, since the joint conductance of the wires is the sum of their respective con- 
ductances, their joint conductance would be i-|-i+i^ |= .5, That is, .5 mho 
would be their joint conductance and, since, again, conductance is the reciprocal, or 
converse, of resistance, the resistance of a conductor having a conductance of .5 mho, 
would be .\ ohm, that is, 2 ohms. In other words, the joint resistance of the said % 
wires in multiple would be 2 ohms. 

The foregoing would be stated, in accordance with the rule for finding joint 
Resistance, as follows : 



-5 

I 



1 1^ ^ ^ ^ =2 ohms. 

¥1-6 + 6" 

Having the foregoing in mind then, the explanation of the law of joint resistance 
of conductors in " multiple " or "parallel" will become plain. It virtually resolves 
itself into this:— First, find the sum of the conductances of the conductors whose re- 
sistances are known, and then ascertain the reciprocal of the sum of those conductan- 
ces, which will be the joint resistance of the conductors. 

The formula for finding the joint resistance of two circuits, e and r, in multiple, 

is generally stated thus : 

KXr . . 

-— r- = joint resistance, 

E— p 

or, for example, assuming e to have a resistance of 20 ohms; r a resistance of 10 ohms, 
as follows : 



30 



AMERICAN TELEGRAPHY 



20X lO 



= X = joint resistance. 



20-f-lO 

This formula is simply the result of working out the foregoing rule, as we mav se^. 
For example, as before, the conductance of r will be 2V ^^^o; that of r, yV mho, conse- 
quently, their joint comiuctance will be — "^ ^' ^^' — "'" — which, by addition of 

fractions, is found to be equal to or =: ioint conductance. Then, as 

^ 20 X 10 R X r *• 

joint co!iductance is the converse of joint resistance, the latter, for two circuits, will 



be represented by the formula just stated: f-^j' • That is, the joint resistance of two 



R X r . 

R +r. 
cij'cuits is equal to the product of their respective resistances divided by their sum. 

The joint resistance of several circuits may also be ascertained, by aid of the lat- 
ter formula, by hrst calculating the joint resistance of 2 of the circuits and then using 
tliat result as if it were the resistance of i wire wherewith to find the joint resistance 
of 3 wires, and tlie joint resistance of 3 wires may then be utilized to find the joint 
resistance of 4 wires, and so on. 

The DisTRiBUTJON OF CURRENT IX DIVIDED CIRCUITS. Tlic law of distribution of 
current in a divided circuit is, in efi'ect, as follows: The strength of current in the 
bi^anches of a dii'ided circuit is inversely proportional to the respective resistances 
of each bi^anch. In other words, the strength of current in each of such branches 
will be found by dividing the potential difference at its terminals by its resistance. 

For exam])le, if, in Fig. 15 /^ we assume the 
E. M. F. of the battery to be 4 volts, and ^he 
resistances of branches a n c to be 4, 6 and 
12 ohms, respectively, the joint resistance of 
which would be 2 ohms, the total current 
strength in the circuit at the poles of the bat- 
tery (neglecting its internal resistance) will 
be, according to Ohm's law, |, that is, 2 am- 
peres, which current will be distributed among 
ABC according to their respective resistan- 
ces. 

Thus A will get |^ = i ampere; b f = f am- 
]>ere, and c y\ = -|^ amj^ere, the sum of which 
fractions of the total current strength is, evi- 
dently, 2 amperes. 

Distribution of current in telegraph wires, in multiple. — The man- 
ner in which the foregoing laws are concerned in the explanation referred to will now 
be considered. 

Suppose the case of a gravity battery of 100 cells, each cell having an internal 
."•esistance of 2^ ohms, making in all 250 ohms, and 4 telegraph wires, each having a to- 
tal resistance of 1000 ohms, connected up with the battery. The joint resistance of 
those wires, as may be ascertained by the rules given, is 250 ohms. 

With all the wires closed at one time the total resistance of the circuit, including 




DISTRIBUTION OF CURRENT, ETC. 3 1 

the internal resistance of the battery will then be 500 ohms. The electromotive force 
of each cell of the battery being aproximately i volt, or 100 volts in all, the resulting 
strength of current yielded by the battery at such times vi^ill be, according to Ohm's 
law, i§S =i, that is .2 ampere. Distributing this current among the four wires 
obviously gives each .05 ampere, since the resistance of each wire is the same. 

With 3 wires open, and i closed, the total resistance of the circuit, including 
as before, the battery resistance, will be 1,250 ohms, which gives a strength of cur- 
rent of nearly, .08 amperes, that is, about yf^ more current than was furnished 
each wire when the other 3 wires were also closed. 

With 10 wires of the same resistance connected to the same battery, the 
strength of current furnished each wire when all are closed, will be, not quite .03 am- 
pere, or about one-third of that which would be furnished any i of the 10 wires 
with all the others open. Assuming that a strength of current of .03 ampere might be 
sufficient to operate the relays, it would be impracticable to keep them adjusted for 
this range of change of current strength. 

With, however, a battery of the same electromotive force, but having a total 
internal resistance of only i ohm, it will make little difference, so far as the strength 
of current supplied each wire is concerned, whether i or all of the 10 wires con- 
nected to it, be open or closed. 

For instance, again assuming each wire to have a resistance of 1,000 ohms. 
With but I wire closed the total resistance of the circuit, including internal resist- 
ance of battery, will be 1,001 ohms. The strength of current in the circuit will be, 
consequently, -^-§-§y = .099 ampere. With the 10 wires closed, their joint resistance 
will be 100 ohms. Adding the battery internal resistance, we get a total of loi 
ohms, which gives i§f ==.99 ampere. This, distributed equally, gives to each of the 
10 wires .099 ampere, as was the case with but i wire closed. If the decimals be car- 
ried out further, it will be found that each wire gets slightly less current when all are 
closed than any one would get with the other 9 open, but, practically, the amount is 
the same. 

With a battery of still less internal resistance, a much larger number of wires 
could be fed without any perceptible change in the strength of current on any of the 
external circuits, regardless of the operation of the other circuits. 

THE DYNAMO-ELECTEIC MACHINE. 

It is easy to construct dynamo-electric machines, having an electromotive force, 
at least, equal to 100 cells gravity, the "internal" resistance of whose "arma- 
tures " is but a fraction of an ohm, and thus it is possible to " feed " from one dynamo 
machine, several hundred telegraph wires, without perceptible variation in the current 
strength furnished. It is this feature, among others, which gives the dynamo machine, 
as a source of electromotive force in telegraphy, so decided an advantage over gravity 
or otlier forms of chemical battery^ in offices where many wires are operated. 

Before entering upon a description of some of the methods by which the current 
established by the dynamo machine is ntilized for telegraphic purposes, it will, per- 
haps, be advisable to state briefly, the theory of the operation of that machine; tliis 
will entail further allusion to some laws of electricity and magnetism. 



32 



AMERICAN TELEGRAPHY 



THEORY OF DYNAMO MACHINES — It is well-kiiown that when a magnet is placed 
beneath a piece of card-board or glass, on which soft iron filings have been strewn, if 
the card be lightly tapped, the filings arrange themselves in symmetrical lines, as 
outlined in Fig. i6. This singular arrangement of the iron filings in the presence of a 
magnet, such, for instance, as that shown in the figure — namely, a bar magnet — indi- 
cates the existence of a force to which the term, " lines of force," has been applied. 



FIG. 16 



FIG. 18. 




^"^^m^^^ 



It is not meant that actual " lines " of force exist; the term being merely used as a 
convenient means of designating the phenomenon and the direction in which the force 
acts. 

It is known also that when a current of electricity is caused to flow in a wire, 
similar magnetic "lines of force" are set up, concentrically, around it, as indicated 
in Fig. 1 7, and, as may be evidenced by passing a wire conveying a strong current 
through a cardboard on which iron filings have been thrown, as illustrated in Fig. 18. 

These magnetic lines of force are set up by what is termed the magnetomotive 

FIG. 17. 




force. The space between the " poles " of a magnet, or wherever its magnetic influence 
is felt, or in the space around a wire conveying a current of electricity, is termed a 
magnetic "field." The substances throus^h which the lines of force pass, including the 
iron of a magnet, compose the magnetic circuit. The expression, number of lines of 
force within a given space, for example, a square inch, is at present generally used in 
practice as a measure of magnetic density, or strength, the term being frequently 
abbreviated to "lines per square inch." 



DYNAMO MACHINE. 33 

The total number of lines of force in a magnetic circuit is termed the magnetic 
flux, and is obtained by multiplying the total area of the field in square inches by the 
density of a square inch section of the circuit. The magnetomotive force is equal to the 
product of the amperes in the coil by the number of convolutions of the coils. This 
is also termed the ampere-turns. The magnetic flux may be increased by increasing 
the magnetomotive force, or by decreasing the resistance, or reluctance, of the circuit. 
Thus the insertion of a soft iron bar in a circuit previously consisting of air alone 
will largely increase the flux, soft iron being a much better conductor of magnetism 
than air (or is more permeable than air). For instance, if the permeability of air be 
1, that of iron may be from 100 to about 350, depending on the quality of the iron. 
The reluctance of iron is not, like ilectrical resistance, a constant, but varies, in 
iron, with the magnetic density of thj circuit. The relation between the foregoing 
terms is shown in the equation: Magnetic flux = ^'^Sctolcf ""'''' ' (^^e page 66.) 

Many of the phenomena of electricity and magnetism are reversible, or converti- 
ble. For instance, it is known that when an electric curient passes in a wire sur- 
Tomiding a soft iron core, the iron becomes a '* magnet." On the contrary, when a 
wire is caused to cross a magnetic field, it is known that an electromotive force is 
developed in the w^ire, which produces a curi'ent of electricity when the ends of the 
wire are connected. It is, however, necessary to the development of such electro- 
motive force, that the wire shall be caused to "cut" the lines of force, in passing 
through the magnetic field. 

In order to assist in comprehending what is meant by " cutting " the lines of force, 
it is usual to assume that these lines are tangible and susceptible of being cut by a 
wire,in some such sense, for instance, as one might cut a falling shower of water with 
a rod. If the wire should be simply moved parallel to the lines of force, that is, 
moved back and forth between the poles of a magnet, no electromotive force would 
be developed in it for the reason that in such a movement no lines of force are cut 
in the sense in w^luch it is found they must be cut to effect that result. 

The electricity, that is, the electromotive force, developed in tlje wire under the 
conditions stated, may be considered to be proportional to the number of lines of 
force cut by the wire in a given time, or to the rate at which it cuts them. For in- 
stance, if a wire cuts i line in one second, and thereby has developed wdthin it an 
electromotive force of, say, i, if it be caused to '' cut " 2 lines in one second, the electro- 
motive force will be doubled ; or, if the density of the magnetic field be so increased 
that, within the same area w^here before there was but i line, there are now 2, and the 
wire is caused to cut them in one second, the resulting electromotive force will be 2. 

In the construction of dynamo-electric machines, the foregoing and other 
facts are availed of. 

As it would be impracticable to secure a magnetic field of sufticient extent and 
density in which to move a wire continuously in a straight line, for the purpose of dev- 
eloping electromotive force, the expedient of rotating the wire in a magnetic field in 
such a way that it will cut the magnetic lines of force, has been most generally 
adopted. The manner in which this result is accomplished, may be explained by the 
aid of the diagrams following:. 



34 



AMERICAN TELEGRAPHY. 



In Fig. 19, a wire loop mounted on spindle x m a uniform field of the magnet n 
s, is shown. This loop may be considered as belonging to one of the coils of the 
" armature " of a dynamo machine, such, for instance, as is used in telegraphy. 

In the "field" the lines of force are always assumed to pass from n to s, in 
which case their direction is said to be " positive." As the field is, in this case, as- 
sumed to be a uniform one, there will be an equal number of lines in any given sec- 
tion of the field in which the loop is placed. In the figure the " lines of force " are, 
for purposes of illustration, supposed to be represented by the straight lines connect- 
ing X s. 

Experiment has demonstrated that when the lines of force are "flowing '' from 
right to left, or from n to s, if the loop be rotated on its spindle so that 
one side, J-, of the loop, is caused to cut the "lines" from a to I? 2, current will 
be set up in s in a direction away from the observer; while the current gene- 
rated, at the same time, in the side s\ in cutting the lines from c to dy 
will be towards the observer. The direction of the currents in the loop, as a whole, 
will, however, coincide, as indicated by the direction of the arrows parallel to s 



FIG. 19. 




and J"'. As the current is the result of an electromotive force established in the wire 
by the act of cutting the lines of force, it is plain that, upon the direction in which 
the wire cuts the lines, depends the polarity of the electromotive force. 

As the loop continues its revolution, and the side s begins to cut the lines from c 
to d, while the side s'^ begins to cut from a to b, there is now set up a current in 
s in the direction opposite to that which existed before it completed the first half of 
its revolution; the same is the case with side s^ of the loop; consequently, the direc- 
tion of the current in the loop, as a whole, is changed at the half of the revolution. 
In other words, the direction of current is changed twice in each revolution, and it 
is, therefore, a so-called alternating current, within the loop. 

Owing to the circular movement of the loop in the magnetic field, it will, in cer- 
tain parts of its revolution, instead of cutting lines of force, simply slide through 
tiiem. This will be when the sides s, s^ of the loop are at right angles to th& 
" faces " of the pole pieces of the magnet, or when parallel to the lines of force, r.s 



DYNAMO MACHINE. 55 

in tlie figure, and as the electromotiv^e force developed in the loop is due to the 
cutting of the lines, it is plain that when the loop is in that position no elec- 
tromotive force is developed in it. Further, for a short distance from the ver- 
tical position the number of lines cut by the loop will be very small, as the motion 
of the sides of the loop is such that near that position it cuts but few lines compared 
with the number it cuts in moving an equal distance as it approaches the hc»rizontal 
position. Consequently, the current not only changes in direction twice during 
every revolution, but it also rises and falls from minimum to maximum strength and 
vice versa, twice in ev^ery revolution, the latter due to the fact that the 
electromotive force rises from zero in the A^ertical position of the loop to maximum in 
the horizontal position, and falls from maximum in the latter position to minimum in 
the vertical position; or, to put it another way, because the coil cuts the mini- 
mum number of lines in or near the vertical position and the maximum number of 
lines in or near the horizontal position. 

A further explanation of the increased or decreased number of lines cut as the 
loop approaches or recedes from the horizontal may be attempted by the aid of Fig. 

In that figure let the horizontal lines between isr and s represent, as before, the 
lines of force passing from the north to the south pole of the magnet. 

Since, as before, the magnetic field is assumed to be a uniform one, there will be 
an equal number of lines in any given section of the space occupied by the field. In tlie 
figure it is assumed that there are 12 lines from a^ to ^^, and 12 lines from b^ to 
r^; that is 12 rows of 12 lines each, making, in the space between the faces of the 
poles isr 8,144 lines. Hence, in making a revolution, each side of the loop will cut 
288 lines, and the loop, as a whole, will cut 576 lines each revolution. In making its 
revolution each side of the loop, of course, describes a circle, equivalent to k in 
Fig. 19. 

By calculating, then, the number of lines cut by each side of the loop in dif- 
ferent parts of its revolution, it is found that, in turning one-eighth of a revolution, or 
through an angle of 45"^, the side s of the loop, only cuts 2 row of lines, that is, 24 
lines, while from 45^ to 90° it cuts, approximately, 4 rows of lines, that is, 48 lines. 
On the other hand, in continuing its revolution from 90^ to 135^ another 48 lines will 
be cut by s^ and from 135*^ to 180*^ only 24 lines. Simultaneously, the side s^ has 
been cutting an equal number of lines at a similar rate of increase and decrease in 
the different parts of its revolution, but in the reverse direction. 

Since, as already said, the electromotive force thus developed m a wire is propor- 
tional to the rate at which the lines are cut, it is evident that the electromotive force 
developed in a loop, or coil, rotated in a magnetic field, may be increased in several 
ways in addition to those previously mentioned. Thus, it may be increased by in- 
creasing the speed at which the loop is rotated. Assuming the loop, Fig. 19, to have 
been rotated at the rate of one revolution, per second, if it be made to turn at the rate 
of three revolutions per second, the number of lines cut per second will now be thiice 
576 lines, and the electromotive force will be trebled. The electromotive force de- 
veloped may also be augmented by increasing the number of " turns ' ' of the wire with- 
out increasing the area or density of the field. For example, if, instead of one 



30 AMERICAN TELEGRAPHY. 

turn of wire, a coil of two turns be employed, each turn of the wire will cut an 
equal number of lines in the course of a revolution, hence, doubling the electromotive 
force, for this practically doubles the number of lines of force cut, per revolution, by 
the loop. 

It is obvious that a current of electricity, constantly varying in strength, alter- 
nating in direction, and circulating in a closed coil, such as has been thus far shown, 
would not, generally speaking, be of much utility, and, therefore, means have been 
provided in the dynamo machine, whereby the current set up in the coil, is con- 
ducted out to an external circuit. In some machines the apparatus for this purpose is 
so arrano;ed that the current is led out to the external circuit, alternatinoj in direction. 
Such machines are termed " alternating" current machines. In others, and among them 
those used for telegraphic purposes, the apparatus employed is such that the current*iu 
the external circuit is in one direction. Machines of the latter class are termed "con- 
tinuous," or "direct" current machines* The plan by which the current is led out from 
the coil in the magnetic field, and the direction of the current made continuous in the 
external circuit is indicated in the case of one coil in Fig. 20. It consists of separat- 




ing one end of the loops of the coil, the terminals of which are connected to curved 
metal segments a, a^ on the spindle of the coil; the segments being insulated from the 
siiaft and from each other. Metal " brushes " b, b are caused to rest on the seg- 
ments, to which brushes the external conductors, leading to any desired point, are at- 
tached. The brushes are placed on opposite sides of the shaft in such a way that, as 
the shaft rotates, each is always on a separate segment. They are also placed on the 
segments in a position corresponding nearly to the point at which the sides of the coil 
will be parallel with the lines of force, namely, at the point where the current is re- 
versed in direction. Thus, as the coil is rotated, the segments pass from one brush to 
the other just as the direction of current is about to change in the coils and, conse- 
quently, each brush is always placed in connection with that side of a coil which 
is generating current in a given direction. Such an arrangement of segments on the 
shaft is termed a " commutator." 



DYNAMO MACHINE. 3/ 

While a current thus "straightened" out would be, as regards the external cir- 
cuit, uniformly in one direction^ it is clear that it would still be very variable as regards 
strength, since it Avould fluctuate from zero to maximum twice in every revolution. 
In order that the current thus generated may be of practically constant strength, as 
well as continuous in direction, many such coils of insulated wire, wound on an iron 
core, somewhat as shown in Fig. 21, are employed in some forms of dynamo machines. 

At one end of this core is a series of metal strips, or segments m, close together, 
but, as in the case of the segments seen in Fig. 20, also insulated from each other and 
from the shaft by suitable insulating material. These segments are arranged cylindri- 
■<jally on the shaft, and form the " commutator." 

The manner in which the coils are connected to the segments and in which 
the coils themselves are wound over the core varies with nearly every type of dynamo 
machine, but the method of winding indicated in Fig. 21 has been frequently employed. 

In that figure, for clearness, but five coils are shown, but the receptacles for others, on 
the core, may be seen. The terminals of the coils i, 2, 3, 4, are, however, shown 
connected to the segments as though the coils lay in adjoining receptacles, as they do in 
practice. One terminal of coil i is brought to segment s^ on the commutator. As 




many turns of wire as may be desired are wound on the core and the other 
terminal of coil i is then brought to the next segment, s^, of the commutator. 
The terminal ^ of coil 2 is also connected to segment s^, wound around the core, and 
then brought to segment s^. A terminal r, of coil 3, is brought to segment s^, and its 
otner terminal is connected with segment ^'*, and so on, around the commutator. 

This arrangement places two terminals of different coils in contact with each 
segment, and starting from any one segment, puts all the coils in series with eacli 
other. But, as the brushes are placed on segments diametrically opposite each other, 
it will be obvious, on consideration, that so far as an external circuit from the bruslies 
is concerned, one-half of the coils are connected in multiple with the other half. 
For example, it may be seen that when, say, segment J*, is under upper brush n, 
the coils 3, 2, I, and the others to the left of that brush, will be in multiple witii 
the coil 4 and the other coils to the right of upper b; and the other end of each series 



a8 



AMERICAN TELEGRAPHY. 



of coils will be at the segment on which the lower brush b may be resting. As, also, 
those jjortions of the coils on opposite sides of the brushes generate currents in 
opposite directions, it is evident that those currents will unite at the brushes and pass 
out to the external conductor. For instance, supposing a current to be flowing ii, tlie 
lower side of coil 3 from left to right, it will pass cut of segment s"^, to wh^ch its 
terminal is attached, in the same direction. In that case the current in the upper side 
of coil c, will be from riglit to left. Then, as the upper sides of coils 3 and 4 are on 
opposite sides of upper bi-ush b, the current in upper side of coil 4, will be from 
left to right, and as the upper part of that coil is also attached by its terminal (/, 
to segment -f*, the currents from both coils will coincide in direction through tlie 
brushes. 

The collection of coils and the core compose the "armature '' of the dynamo ma- 
chine. Iq practice the brushes are jjlaced on the commutator at, or near the point where 
the reversal of polarity in the coils takes place. A shaft s, to which the armature is 
rigidly attached, passes through the centre of the latter. Tlie shaft rests on the 
usual bearings, and in practice it is equipped at one end with a pulley by means of 




which the armature is caused to revolve rapidly between the poles of the magnet. 

The magnet used to produce the magnetic field in which the armature rotates, is 
termed the ''field magnet." Occasionally, permanent magnets have been used as 
" field " magnets, but ordinarily, electro-magnets are employed for the purpose. 

A primary battery may be used to supply the current necessary to magnetize the 
field magnets but it is generally obtained by the simple device of " shunting" a portion 
of the current developed in the armature coils through the field magnet coils c^, 
c^, in the manner shown in Fig. 2.^, in which, for simplicity, only one coil c of the 
armature, is shown, and in which figure m, m are the field magnets, and b, b^ are the 
brushes, on the commutator. The manner in which, this magnetizing current is devel- 
oped may be described as follows : 



DYNAMO MACHINE. 



39 



In the iron of the magnets there usually is some "residual" magnetism from 
previous magnetizing. When the iron is thus slightly magnetized a weak magnetic 
iield is set up between the poles of the magnet. As the armature revolves slight elec- 
tric currents are *' generated " in its coils. These pass out to the brushes. Here the 
current divides, one portion passing to the external wire, and another through the coils 
of the " field '' magnet. This current, in passing through these coils further increases 
the magnetism of the field magnets, and thus the magnetic field is increased. This 
still further increases the current in the coils of the armature and, consequently, a cur- 
rent of greater strength flows in the field magnet coils, which in turn still further in- 
creases the magnetic field, and so on, until the maximum electromotive force which 
the dynamo macliine may- be capable of developing is reached. 

Machines of this class are termed self-exciting. Machines wound in this way are 



FIG. 2-^. 




known as shunt-wound dynamos. In some machines the field magnets are excited by 
separate machines, an instance of which will be given later. 

The essential parts of a dynamo machine are the field magnets, armature, com- 
mutator and brushes. These parts are shown in Fig. 23, which represents the " Edi- 
son " type of dynamo machine, referred to. a is the armature, one end of which only 
is seen, i and 2 are the brushes resting on the commutator. The coils of the field 
magnets are indicated by c, c. The cores of the field magnet by b, b, which are 
connected at the top by the cross-bar b of soft iron. The pole pieces of the field mao-_ 
net N s, are curved as shown, and between the pole pieces the armature is placed. 
The curved faces of the pole pieces are so arranged that the armature is partly envel- 
oj^ed by them. This is to insure the passage of the coils of the armature througli the 
maximum number of lines of force, and also to reduce the resistance of the mao-nelic 



40 AMERICAN TELEGRAPHY. 

circuit by reducing the resistance of the "airspace" between the poles. For the 
same reason, also, the core of the armature is made of iron, which, being a far supe- 
rior conductor of magnetism than air, concentrates, or directs, the magnetic lines of 
force through the coils, or, it may be, adds its lines to the circuit. See page 66. 

The practical, or working unit of electromotive force is developed when a conduc- 
tor cuts 100,000,000 lines of force per second. This unit is termed the volt. In prac- 
tice it is not uncommon to have '' fields " of a density of 165,000 lines per square 
inch. 



METHODS OF ARRANGING DYNAMOS IN TELEGRAPHY. 

In practical telegraphy the lengths and resistances of circuits vary very materi- 
ally, so that, when gravity battery is used as the source of electricity, the number of 
cells of which a battery is composed is usually governed by the length and resistance 
of the circuit to which it is to be assigned. For instance, a single wire from New 
York to Boston, 300 miles, might require 75 cells; one, New York to Buffalo, 430 
miles, 150 cells; one. New York to Philadelphia, 150 miles, 50 cells, while quadru- 
plexed circuits between the same points may require 150 cells, 350 cells, and 125 cells, 
respectively. 

One method of arranging dynamo-electric machines to furnish varying electromo- 
tive forces, is shown in Fig. 24, which illustrates the plan of the original device for 
that purpose, as designed by Mr. S. D. Field. Practically the same arrange- 
ment is now in operation in some of the Western Union Telegraph Company's 
main offices. 

The dynamo machines shown are known as the " Siemens-Alteneck.'' The field 
magnets are indicated by the letter m in each case; the armatures by a. The ma- 
chine E is called the "exciter." It is self-exciting. Its function is to excite the field 
magnets of the machines a, b, c, d, which furnish the current for the wires. 
The circuit from machine e simply extends to and through the field coils of the other 
machines and returns to e. This machine is wound in what is termed " series "- — 
that is, the field magnet coils are connected directly in the external circuit and with 
the armature coils, not shunted as in Fig. 22. Each of the machines a, b, c, d, is ca- 
pable of developing an electromotive force of about 80 volts, and, therefore, as one 
machine is connected to the other in series, in the same manner as chemical battery 
cells might be connected, the total electromotive force developed by the four machines 
is 320 volts, as indicated in the diagram. The circuit of the machines a, b, c, d 
is from earth e^, thence to the lower brush of a, through the armature to the upper 
brush, thence to point x^ where part of the current is diverted to the line wires of low 
resistance, (first passing through an artificial resistance k.) The other portion of the 
circuit leads to the lower brush of machine b, at which machine the e. m. f. is 
augmented to the extent of 80 volts, making 160 volts, From the junction x'^ a wire 
leads to the switch board to furnish current to such line wires as require 160 volts 




^ 

^ 






I 



^ 

^ 




42 AMERICAN TELEGRAPHY. 

potential. The circuit then, from ^i, passes through, in the same way, the armatures 
of c and D, still further increasing the e. m. f., which is utilized as in the cases of a 
and B. 

It is evident that machine a must furnish a larger amount of current than any of 
the other machines, since it supplies a share of the current furnished to the wires from the 
2d, 3d, and 4th potential, as well as all the current supplied to the wires drawing 
from the ist potential. This it does, owing to its low internal resistance, which 
is about |- of an ohm, without any appreciable variation in the strength of current 
furnished the wires, regardless of whether but one or several hundred wires are being 
"fed." 

The resistances r e, etc, are of German silver wire coiled around a cylinder of 
plaster of Paris. Each coil rests on a plate of metal, to which the wire leadino- from 
the dynamo is attached. One of these coils is inserted in the circuit of every w^ire. 
The function of these coils is to diminish the current strength, thus avoiding 
sparking at keys, etc , in cases of short-circuiting. 

As in the operation of the polar duplex and the quadruplex systems it is essential 
to have reversals of electric polarity, and as it is not practicable, when a machine is 
furnishing electromotive force for a large number of wires, to reverse the dynamo 
machines, means to provide for this essential must be devised. 

This is accomplished by operating two series of 5 dynamos each, one of which 
series is caused to furnish positive polarity, the other series, negative polarity. To 
guard against failure of one of the series, a third series of 5 machines is held in readi- 
ness as a " spare" series. Suitable devices for converting the spare series into a pos- 
itive or negative polarity series, are provided in the dynamo room, but as means for 
effecting this result will be described more in detail in the description' of the present 
dynamo plant in the Western Union building, New York City, it will suffice to state 

FIG. 25. 




DYNAMO REVERSING SWITCH. 



here that this result, namely, the conversion of the spare series into a positive or 
negative series, can be readily accomplished by placing a reversing switch in the field 
magnet circuit of the machines, since a cliange in the direction of the current through 
the field magnet coils of the machines will result in a change in the magnetic polar- 
ity of the field magnet, which change will, in turn, by reversing the direction of the 
magnetic lines of force in the field, reverse the direction of the current generated in 
the armatures of the machines a, b,'c, d; the direction of the current through e, of 
course, remaining uniform. 

Such a switch is outlined in Fig. 25, in which e is a dynamo machine, i, 2, 3, 
4, 5, 6, are metal discs. With the plugs as shewn, the current through- the field mag- 



PYNAMO MACHINES. 



^3 




44 



AMERICAN TELEGRAPHY. 



net circuit f is as indicated by the solid line arrows. With the plugs inserted at 3 and 
4, instead of at i and 2, the current in the field magnet circuit would flow as shown 
Ijy the dotted line arrows. 

In Fig. 26 is shown, theoretically, the present arrang^-ment of th^ dynamo 
machines employed in developing electricity for the wires emanating from the 
Western Union building, New York. It differs in several respects from the arrange- 
ment just described. In the former there are but four grades of potential, although, 
five machines are employed. In this arrangement there are five grades of poten- 
tial, each machine of a series being utilized to develop current for the line vires. 
These machines are of the "Edison" type and manufacture. The ist and 2** ^na- 

FIC, 27. 




chines of each series, Fig. 26, supply 70 volts each; the 3d and 4th machines 60 volts 
each, and the 5th machine 65 volts; amounthig in all to 325 volts for each series. 
Each machine is tapped at x^ x, etc. as in the diagram, and a portion of the current 1? 
diverted to the artificial resistances, consisting of one or more incandescent lamps, and 
thence to the line wires at the switch board, practically as in Fig. 24. 

The 5th machine in the figure is shunt wound; all the others are wound with sep- 
arate field magnet coils. The 5th machine is self-exciting. The other four machines 
are excited by the 5th machine which, in addition to furnishing 65 volts for line 
wires, also supplies current for its own field magnet, as well as the field magnets of 
the other machines. The field magnet coils of the ist, 2d, 3d, 4th and 5th machines 
are connected in multiple as shown. In the field magnet circuit of each of the five 
machines, a resistance k is placed. This resistance is varied to increase or decreas^- 
the field magnetism when it is desired to vary the electromotive force of a machine. 



DYNAMO REVERSING SWITCHES. 



45 



The resistance of each field magnet coil is about 30 ohms; that of each armature about 
.09 ohm. 

As in the Field arrangement, previously described, there are also three series, of 5 
machines each, in this arrangement; two of which series are permanently arranged to 
furnish positive and negative polarity, respectively; the third is a "spare" series, 
which, by means of a " reversing " switch may be caused to develop positive or nega- 
tive ]3olarity as required. 

The manner in which this change is effected is shown in Figs. 27 and 28, in 
which figure but two machines of the spare series are shown, they being sufficient to 
indicate the plan, s is a switch consisting of the brass strips i, 2, 3, 4 — i, 2 and 3, 4 
being metallically connected, b and b^ are bars of metal, pivoted on the supports, a 

FIG. 28. 




3fecckuie3 

A^, respectively. Tlie wires from the 5th machine are led to a a^. The bars b b^, 
are rigidly connected together by an insulated cross-bar and handle s, by means of 
which those bars may be turned over on their pivots, or hinges A a^, from the lower 
strips, 2 and 4, to the upper strips, i and 3, and vice versa. 

Upon the position of the bars b b^ depends the direction of the current from the 
"spare " series. In the position shown in Fig. 27 it is assumed that the series is fur- 
nishing positive polarity. 

When the bars are connected with strips 3 and i, as in Fig. 28, it will be found 
that, wliile the current flowing from the 5th machine is still in a positive direction, tlie 
current which it supplies to the line wires, via strip 2, is in a negative direction. At 
the same time, owing to the change in the direction of the current flowing through the 



46 AMERICAN TELEGRAPHY. 

field magnets of the other machines, due to the changed position of the bars b b^, the 
current flowing from those machines to the wires is in a negative direction. This is 
assuming that the current flowing outwards from the upper brushes indicates a posi- 
tive polarity, or direction of the current. 

An amplification of this switching arrangement is shown in Fig. 29, which 
figure illustrates, besides, the practical connections of the machines, with the further 
means required to speedily change from either of the 'permanent" series to the 
"spare" series, sw is a switch board. The discs i, 2, 3, 4, 5, on sw, are large, 
metallic discs of ordinary form, with semi-circular notches to receive metallic j^lngs. 
Discs I, I, I, I, I, are connected to the wires leading to dynamo machines of the re 
gular positive series. Discs 2, 2, 2, 2, 2, are connected w^ith the wares leading to 
switch board or line wires; discs 3, 3, 3, 3, 3, with the machines of the spare series 
(two of them via the commutators, or reversing switch s) and discs 5, 5, 5, 5, 5, with 
the "permanent," negative series, of machines. Discs 4, 4, 4,4. 4, are also connected 
with wires leading to the switch-board in the operating room. 

In the figure, discs 2, 2, 2, 2, 2, and discs 3, 3, 3, 3, 3, are connected together by 
plugs. So also are discs 4, 4, 4, 4, 4, and 5, 5, 5,5, 5. This places to the wires tlie 
" permanent " negative series and the spare series furnishing positive polarity. If 
it is desired to release the " sj^are " series and to place in operation the permanent, or 
regular, positive series, plugs are first inserted between discs i, i, i, i, i, and 2, 2, 2, 
2, 2. This places the two series in parallel. When tliis has been done the plugs be- 
tween 2, 2, 2, 2, 2, and 3, 3, 3, 3, 3, are then removed, freeing the spare series. Should 
it be required to release the regular negative series, the commutator s is so placed 
as to cause the spare series to become negative, after which plugs are inserted be- 
tween discs 4, 4, 4, 4, 4, and 3, 3, 3, 3, 3. This also places the spare series in parallel 
with the regular negative series, whereupon the plugs may be withdrawal from 
between 4, 4, 4, 4, 4, and 5, 5, 5, 5, 5; thereby releasing the regular positive series. 
By thus running like series in parallel, momentarily, no break is caused in the line 
wire circuits. Resistances, amounting to about 2.5 ohms, per volt of electromotive 
force are placed between the dynamo machines and each wire circuit, for the rea- 
son already stated. These resistances are "incandescent" lamps. They were substi- 
tuted for the coils of German silver wire because of the frequent breakages of the fine 
wire of the coils, which occasioned delays. The lamps have been found to give satis- 
factory service. 

Another arrangement of dynamo machines for telegraph purposes, differing from 
those already described, is shown theoretically in Fig. 30. It is in use in the main of- 
fices of the Postal Telegraph Company, New York City and elsewhere. In this ar- 
rangement of the dynamos the machines are not connected in series, but each 
machine is operated separately, as shown in the figure. Each machine may be con- 
sidered as the equivalent of a gravity battery of very low resistance, out of which 
a large number of wires are "fed.'* In the New York plant there are 16 machines 
furnishing eight grades of negative and positive potential, namely, 50, 70, 90, no, 
200, 250, 275 and 300 volts, respectively. In the figure, 6 machines are show^i, 3 
negative and 3 positive. One pole of each machine is connected to ground, the 
other pole is connected to a switch s, and thence to the wires. By means of this 




myes 



7b JyCres 



48 



DYNAMO MACHINES. 





I 



LOCAL DYNAMO MACHINE. 



49 



switch any machine can be readily disconnected and another substituted. Two sp^ire 
machines are provided and these have switches so connected that the line wire termi- 
nal and ground terminal may be readily transposed to furnish a desired polarity. A 
resistance k^ r^ k^ consisting of German silver wire, is inserted in the circuit of each 
wire before the operating room switch is reached. The machines are of the " Edison " 
type, shunt Avound. The electromotive force of each machine may be varied by the 
removal or insertion of resistance from the rheostat r in the field magnet circuit. 
The machines are driven by a suitable motor. To prevent injury to the appara- 
tus, due to accidental short-circuting, /uses r are inserted in each dynamo circuit at 
the switch s. These fuses "blow" out under a "heavy " current, thereby opening 
the circuit. 

In several large telegraph offices the /oca/ ciYGuits are now operated by current 
furnished by dynamo machines. 

In some cases where this has been done, the sounders have been wound to about 40 
ohms, and the dynamo machine has been designed to have a very low internal resis- 
tance, which is rendered necessary by the fact that all the sounders are connected in 
multiple and, hence, a very low, joint resistance of the combined external local circuits 
results. This will be clear upon a reference to Fig. 31, in which l b is the local 
dynamo machine, and c the combined local circuits with the sounders s in multiple. 

FIG. 31. 




DYNAMO ARRANGEMENTS FOR " LOCALS." 

Assuming that there may be 800 sounders in a large office. This at 4 ohms each 
would give a range in the resistance of the external circuit c of, from 4 ohms, when all 
but one of the sounders are open, to five thousandths of an ohm when all the sounders 
are closed. With the sounders wound to 40 ohms, the lowest external resistance 
would be five hundredths of an ohm. The /«/<?r«^/ resistance of the dynamo machine 
is the resistance of the wire of its armature; (or the joint resistance of its wires). 

The dynamo machine is also used quite extensively in large cities in the service 
of " stock" and "news" quotation companies. When that is the case, they are ar- 
ranged in practically the same manner as in the case of the regular telegraph service. 



49^ AMERICAN TELEGRAPHY. 

Motor-Dynamos. — Since the foregoing was written what are termed motor-dyna- 
mos have come somewhat extensively into use in telegraph ojffices for the purpose of 
obtaining current for the charging of storage batteries as well as for the operation of 
main and local circuits direct. Philadelphia W. U. office is an instance of the latter use. 
On page ^^ attention is called to the fact that many of the phenomena of electric- 
ity and magnetism are reversible. Another instance of this reversibility is afforded in 
the oftse of the dynamo machine, which, when a current of electricity is sent through 
its coils from an outside source at once begins to turn around. The explanation of 
this may be considered as follows : Assuming that the dynamo machine is shunt or 
series \\ound, the current, or a shunted portion of it, which passes into its armature 
also flows through the field magnet coils, thereby setting up a magnetic field 
practically as indicated in Fig. 19. A magnetic field is also established around 
those coils of the armature through which the current is passing, and these coils 
will obviously be those upon which the brushes are resting. If, therefore, the 
brushes are set at such a point on the commutator that the magnetism set up around 
the armature coils does not coincide with the magnetism of the field, the tendency 
will be for the armature to be attracted into a position where the respective magnetic 
lines of force will coincide, but the moment the armature turns, the armature 
coils which were carrying the current from the brushes slip past the brushes and 
another set of coils is brought into action and the current dies out of the first set 
of coils. It is then clear that the same tendency of the lines of force from the 
new set of armature coils and those from the field, to coincide, still exists, and, hence, 
the armature continues to turn, with the result that another set of coils is called into 
play, and so on, a sort of tread-mill arrangement as it were. 

If a belt be attached to the pulley of the dynamo machine it may be caused to do 
work and it is then termed an electric motor. In some cases instead of a belt being 
attached to its pulley, the shaft of a dynamo machine is attached to the motor and 
the latter in this way rotates the dynamo machine. When connected in this way the 
combination forms one type of motor-generator, or motor-dynamo. 

Another form of motor-dynamo is one in which the armature coils of the motor 
and those of the dynamo machine are wound on one core. But in this case the arm- 
ature is furnished with two commutators, one at each end, for the dynamo and motor 
coils, respectively, as in Fig. 31a. The current from the outside source enters the 
armature coils of the motor causing the armature to rotate as before. As now the 
dynamo coils are caused to rotate in the magnetic field of the field magnets, an elec- 
tromotive force and current are established in those coils, which will be proportional 
to the density of the ma^jnetic field, the number and length of the coils and also to 
their resistance, as well as the speed of rotation, as already explained, page 35. This 
being known, it is a comparatively easy matter to design a motor-dynamo to be oper- 
ated at any stated voltage from the outside source applied to the motor, and to deliver 
at the dynamo terminals any desired electromotive force and current. 

The utility of such a device in telegraphy and in other branches of electricity is 
that the electromotive force and current from an electric light or electric power plant 
may be availed of to drive a motor which in turn will drive a dynamo machine con- 
structed to furnish a suitable electromotive force and current for telegraph purposes.* 



STOKAGE BATTERY. 

Storage battery. — The storage cell as now constructed and used in telegraphy 
and for many other purposes, consists of prepared plates of lead immersed in a liquid 
solution of sulphuric acid and water ; about five parts of water to one of sulphuric 
tvcid. What are termed the positive plates are all connected together; similarly those 
termed the negative plates are likewise connected. The plates are placed side by 
side, one negative next one positive, and each plate is separated from the other by 
thin sheets of asbestos cloth. A metallic lug projects from each plate above the so- 

* In Philadelphia one motor-dynamo, receiving current for the motor portion from the street electric mains, 
at about 220 volts potential, is set apart for each positive and negative potential required, piactically akin to the 
arrangement shown in Fig. 80, but the Field Key system is used in the quadruplex systems as usual. Of course 
the machines in Fig. 30 are supposed to be belt driven. 



STORAGE BATTERY. 



49^ 



lution, and by these lugs the positive and negative plates are respectively connected 
as stated, and virtually as shown to the right of Fig. 31a (chloride cell). The number 
and size of the plates in a cell depend upon the desired capacity of the cell. This ca- 
pacity is rated in ampere hours. Thus if a cell should give out 20 amperes of current 











FIG. 31^. 




ELECTMIC LIGHT CJRCUTT 






Mot 


» 


Auiom^cxiic Cut Out 




Mfu 


I 




* 


^JW-^ 



Siorcc^e Cells 




%0 Cells 



CAloride Cell'' 



\ -h 




"strength, without becoming unduly discharged, for one hour, it would be said to have 
a capacity of 20 ampere hours. This same cell, however, might give out 40 amperes 
for half an hour, or 10 amperes for 2 hours. 

These batteries (sometimes called secondary batteries) derive their name from the 
fact that electricity is, so to speak, pumped into them and there stored until required. 
This is called charging the cells. In charging, the positive pole of a dynamo machine is 
attached to the *' positive " plates of the cell and the negative pole of the same machine 
to the negative plates of the cell. When the dynamo is removed and the positive and 
negative plates are connected by a wire a current flows from the positive pole, in other 
words, in a direction opposite to that of the current which charged the cell. In reality 
the plates which were attached, in charging, to the positive pole of the dynamo are the 
negative plates, and those connected to the negative pole the positive plates, anala- 
gously as the zinc element in the gravity cell is the positive element of that cell, but 
it is the practice to refer to the plates connected to the positive pole of the dynamo as 
the positive plates, and, contrariwise. A battery of primary cells could be employed 
to charge a storage battery, but it would not be economical to do so on a large scale. 

Although termed stora^^e batteries it is, of course, known that, in fact, electricity 
is not stored up in these cells, but only the energy of chemical change. For, if after 



49^ 



AMERICAN TELEGRAPHY. 



320 VoJis 



D 2? • 














IL 











240 VoZU 



ibo VoZia 



JL' 



the cells fire charged, the plates should bs removed from tho solution of the cell, no 
iadication of electricity would be perceived. The action that takes place in the cell 
daring charging is a chemical one and a chemical action accompanies the discharge of 
the cell. 

FIG. 3i(^. In the first storage cells which were exper- 

320V011S imented with, the plates consisted of ordinary 
thin sheets of lead placed in the solution men- 
tioned. The effect of sending a current of 
electricity through the electrolyte (the solu- 
tion) of these cells may be considered as fol- 
lowt-, namely : the decomposition of the water, 
releasing oxygen aud hydrogen ; the oxygen 
240 vbm ^^ ^j^^ positive pole of the charging current 
ri I ||||||||| uuiting with the lead to form peroxide of lead, 

and the hydrogen settling upon the plate at 
the negative pole. On removiug the charg- 
ing current and connecting the terminals of 
the plates a current flows from the positive 

B' B itoVoiu pole, and during this time the peroxide of 

lead gives up its oxygen which reunites with 
the hydrogen, forming watei'. In other words 
the current flows until the plates ai d electro- 
lyte resume their previous chemical condition. 
Measurements have shown that the difference 
^oiu ^^ potential of these plates is about 2.4 volts. 
That is, the real positive plate is c lectro posi- 
-|- tive to the peroxide of lead plate to that ex- 
tent. 

After the cell is discharged it is found that 
a change has taken place on the surface of 
the "positive "plate, namely, that the metallic 
lead precipitated from the peroxide has be- 
come spongy, or porous, while but little change is noticeable on the negative 
plate. By reversing the direction of the charging current and repea'ing this 
procedure for a considerable time it is found that the capacity is conhiderably in- 
creased, but this method could not be continued indefinitely as it would obviously 
lead to the disintegration of the plates. Improvements in the construction of the 
plates have therefore modified this method of "forming " the plates. For example, in 
the type of cell known as the "chloride," which is now extensively used in telegraphy 
and otherwise in this country, the plates (Fig. 3i«) consist of specially prepared gran- 
ular or porou-i lead tablets, in square and circular form, surrounded by ordinary pure 
lead which has been moulded around these tablets under pressure, the whole forming 
a com acfc plate.* This cell derives its name from the fact that the porous lead usea 
for tiie tablets is obtained from chloride of lead; there is no chlorine used in the cell 
aff. ^r it IS ill actual operation. After the plates are thus compressed the plates which 
are inten.Jed to serve as positive plates are immersed in a solution of sulphuric acid 
through which an electric current is passed in one direction for about fourteen days, 
oy which time the granular lead has been converted into peroxide of lead, or, 
as it is said, into active material, when the plate is ready for setting up with the neg- 
ative plates in the cell. In this cell the tablets for the positive plates are made in 
circular form ; tho-^e for the negative plates in squares. In a solution of sulphuric 
acid, lead is normally attacked by the acid, forming sulphate of lead (PbS04), and if 
the action is prolonged a higher su'phate, or "sulphating," as it is lerjued, 
which is indicated by a whitp scale on the h a<1, ensues, more or less impairing the 
cell's utility. Too strong solution and over-discharging also conduce to sulphating. 
According to some authorities, the simple sulphate of lead facilitates the operation 

* In tbe latest type of this cell the tablets are formed out of a strip of con ugated lead about ^4 inch, in widtll, 
which is rolled into a circular tablet about y^ inch in diameter, the corrugations giving a larger surface. 






STORAGE BATTERY. 49^ 

of the cell. From this standpoint the chemical action that takes place in the storage 
cell is considered to be as follows : The lead sulphate during charging is broken up 
into peroxide of lead (Pb02) which is deposited on the positive plate, and into metallic 
lead (Pb) which is deposited on the negative plate, while sulphuric acid (H2SO4) is lib- 
erated in the electrolyte. The action in discharging is the reverse of this, leading to 
the reforming of lead sulphate. 

Hence, in charging the cell the solution increases in density as sulphuric acid is 
released, while, in discharging, it becomes less dense. Within certain limits the elec- 
trical resistance of sulphuric acid solution decreases as its density increases, and 
these limits are virtually maintained in practice. As, however, the electromotive force of 
the cell is highest when fully charged, and falls somewhat as it is discharged, it is con- 
sidered advisable to allow the density of the solution to exceed the point at which it is 
the best conductor, so that as the electromotive force of the cell falls in discharging, 
the resistance may for a short time fall, whereby a better average electromotive force oi* 
the cell is obtained. The electromotive force of the cell, as stated, when fully charged 
is about 2.4 volts. In discharging it should not be allowed to fall below 1.9 volts. 
The average is about 2 volts. In all storage cells there is one more negative plate 
than there are positive plates ; thus the positive plates are enclosed at both ends of 
the cells. It will be understood that, regardless of the number of plates in a cell, 
the voltage is practically the same. Consequently, to get a suitably high electro- 
motive force, the negative plates of one cell are connected to the positive plates of 
another cell, or vice versa, as in the case of any primary battery. 

One of the ways in which the cells are charged and utilized in telegraphy is out- 
lined in Figs. 3 1 a, 3 1 ^. In these figures it is assumed that the voltage on the electric 
light mains is not suitable for the charging of the cells and, consequently, a motor- 
transformer is operated by the current from those mains. The dynamo portion of 
the machine is arranged to generate an electromotive force of no volts. This then 
may charge several banks of cells, say, 4 banks of 40 cells each, in multiple. These 
cells may then be connected up in series by suitable switching devices and resistances 
to furnish electrical pressures for the main wires varying from, say, 80 to 320 vo ts as 
indicated in Fig. 31^ ; each series of cells a, b, c, d, and a', b', c', d', acting practically 
as the dynamo machines shown in Fig. 26. 

Similarly a motor-dynamo may be utilized to charge cells for the local wires and 
instruments. In the latter case the dynamo coils of the machine would be designed 
to generate a much lower voltage, but much greater quantity of current. This in 
turn charges ce Is of greater capacity. The capacity of the main Ime cells may range 
from 72 ampere hours to 50 and 25 ampere hours, the cells a a' in the figure, for exam- 
ple, being called upon for more current than the cells b, b', for the same reasons as 
are given oq page 42. The capacity of the cells for the locals is about 250 ampere 
hours. The manner in which the locals are connected in this service is analogous to 
the method shown on page 49, Fig. 31. Of course the actual capacity of the cells for 
main line and local service will vary with the special needs of each case. The internal 
resistance of these cells is obviously very low, to which is due the large current which 
they supply, and also the ability to supply many wires from one battery. {See 
page 31.) The internal resistance is readily calculated by Ohm's law, viz.! e = e ^- a 

It is evident that after the storage cells are charged, or partly charged, they exert 
a counter electromotive force against the dynamo machine. Consequently it is essen- 
tial that the potential of the machine shall always exceed the combined pressure of ail 
the cells that are in series, otherwise the tendency would be for the cells to drive the 
dynamo as a motor, or perhaps to short-circuit themselves through its armature. To 
prevent such occurrences a simple automatic circuit-breaker, or cut-out, is used, as outlined in 
Fig 31a. This consists of a soft iron core with pole-pieces p. Only one pole-piece is shown. The 
core is surrounded by a few turns of heavy wire w, the two ends of which dip into cups m con- 
taining mercury. The cups and heavy wire normally form part of the dynamo-circuit. The core, 
with its turns of wire, is suitably pivoted and the pole-pieces tend by gravity to fall away from 
armature a. While the normal current flows the pole-pieces a-e attracted, but wiien from any 
cause the current ceas-s, or very measurably diminishes, the pole-pieces drop, thereby lifting 
the wires w out of the mercury and the circm't remains broken until the cut-out is reset." 



CHAPTER IV. 

THE MORSE TELEGRAPH SYSTEM. 

Theokt. — The Morse telegraph system and, with but one or two exceptions, the 
other electrical telegraph systems described herein, primarily depend for their suc- 
cessful operation- upon the fact that when a current of electricity flows in a coil of in- 
sulated wire surrounding a soft iron bar, the bar becomes a magnet (termed an elec- 
tro-magnet). When the current ceases to flow in the wire, the bar of soft iron ceases 
to be a magnet. Following that is the fact that when a piece of soft iron is presented 
near a magnet there is a mutual attraction between them which tends to bring them 
together. That the attraction is mutual is evident from the fact that if the piece of 
iron be free to move while the magnet is held, the former will approach the latter, 
wliile if the magnet be free to move and the iron be held, the reverse will be the case. 
The supposed cause of this attraction will be stated presently. 

We have already seen (Chap. HI.) that so-called magnetic " lines of force" exist 
in the presence of a magnet. Also that, surrounding a wire conveying a current, sim- 
ilar magnetic lines of force are found, and that these lines, in availing of the jDresence 
of a magnetic conductor, such as soft iron, permeate and give it the properties of a 
magnet. 

Faraday, who discovered and named this phenomenon, assumed that the tendency 
of the lines of force is to coincide in direction, and to contract, or shorten themselves. 
This assumption may be used to explain the action of a magnet, such as a "relay' ■' or 
a "sounder,".in attracting its " armature:" The lines offeree emanating from the poles 
of the magnet enter the iron armature, the iron becoming, as it were, the vehicle of 
thj lines of force. Then, as, according to the foregoing theory, the lines tend to 
shorten themselves, as does, for instance, a stretched elastic band, the armature is 
drawn and held towards the poles of the magnet, even against the pull of a retractile 
spring, as long as the iron continues magnetized. 

In some of the following chapters reference will be made to the fact that there 
is mutual repulsion between the north poles of magnets when presented to each other, and 
that between south poles of magnets there is also repulsion under similar conditions. 
This effect, it m.ay be added here, is also explained by the foregoing assumption, 
namely, that the " lines of force " tend to coincide in direction. It is, apparently, the 
attempt of the lines issuing from the similar poles of each magnet to so turn the 
lines of the other pole that they shall coincide in direction with its lines that git'es 
the mutually repellant effect referred to. 

In order to obtain the " flow " of current necessary to magnetize the 
iron bar surrounded by an insulated coil of wire, the " circuit" of the wire must be 
complete, and a source of elecU'omotive force must also be provided. 

A " circuit" may be represented, as in Fig. 32, by a line, or wire w, battery b 



THE MORSE TELEGRAPH SYSTEM. 



51 



and a galvanometer, g, which is an instrument devised to indicate the presence of au 
electric current in a circuit, {see Galvanometers). 

The source of electromotive force, in this case battery b, is represented by the 
thick and thin lines, the usual symbols of a voltaic cell, or battery, in electrical dia- 
grams; the thin line representing the positive pole, the thick line the negative. 

FIG. 32. 




The course of the circuit is assumed to be from the positive pole of the cell, or 
battery b, and thence through the wire w, the galvanometer g, and back, through the 
battery, to the positive pole. When key k is down, or " closed," as in the figure, the 
circuit is completed, and a continuous current flows; when the key is raised, o^' 
*' open," the circuit is open and the current ceases flowing. 

An ordinary telegraph circuit without instruments is theortically shown in Fig, 
^2,' In this case the circuit comprises the battery b, the line wire and the ground. 
The course of the circuit is assumed to be from the ground at x, through the battery, 
and the line wire to the ground at t. When the wire is continuous from the gr .und 
at one end, to the ground at the other, the circuit is said to be completed, and a cur- 
rent will flow in the wire as indicated by the arrows. 



FIG. 33. 



y 



^ — wMk 



Ground 



Orvccnd. 



It has for years been a disputed point whether the earth acts as a conductor to 
" conduct" the current from the terminal at one station to the terminal at the other 
station, thereby completing the circuit in the sense that it would be completed by a 
wire; or whether the earth acts simply as a large reservoir out of which, so to speak, 
the electricity is pumped into the wire at one end, and out at the other end, as water 
might be,if, for instance, the wire were a tube with one of its ends in Boston harbor 
and tlie other end in New York harbor. In the latter case, obviously, with suitable 
pumping apparatus, there might be a constant flow of water through the tube from 
Boston to New York or contrariwise, without causing any perceptible flow of water 
in the ocean, beween those points, as a result of the water pumped through the tube. 



^2 



AMERICAN TELEGRAPHY. 



But, for practical purposes, this is immaterial, inasmuch as the fact remains 
that, when the wire is thus placed in the earth at both terminals, no matter how 
widely separated, the circuit is practically completed, virtually as though the cir- 
cuit were completed by a return wire. 

A circuit such as shown in Fig. 32, in which the circuit is completed by a wire, is 
termed a " metallic" circuit. One such as that shown in Fig. ^t,, in which the earth 
is used to complete the circuit is termed a " ground return " circuit. 

Operation morse system. — Since the Morse telegraph system is based on tlis 
foregoing facts, and since it employs them to transmit signals electrically by the open- 
ing and closing of a circuit for a longer or shorter interval, which acts operate apparat- 
us designed to automatically record or to convey those signals to an operator at a remote 
station, it is evident that,to insure the successful operation of that system, there must 
be provided, among other things, a circuit capable of being readily opened and closed ; 
a source of electricity; a magnet capable of being quickly magnetized and demagne- 
tized , and a piece of soft iron free to move to and from that magnet; which provis- 
ion we shall see has been made. 

The essential apparatus of a Morse telegraph equipment, for one circuit, at one sta- 
tion, consists of instruments termed a relay, a sounder and key; besides a local bat- 
tery to operate the sounder, and, if the station is a terminal one, a main battery con- 
sisting of from 10 to 150 cells or more, according to the length of the circuit. 

A regular Morse circuit with battery, keys, relays and sounders, at two terminal 
stations, is shown in Fig. 34. r, e, are the relays, each of which is furnished with 
a bar s of soft iron, termed the core. This core is surrounded by a coil of small insu- 
lated, copper wire, which is generally protected from injury by a hard rubber sleeve. 



FIG. 34. 



ri 



H 



I — ^#— 



-^ 



I fii 1 1 1 Wi 
rv I 1 1 I 1 ffn 









X 



y^cu.^ty l./rt,&' 




THEORETICAL MORSE CIRCUIT. 



The poles of the core are at the ends next to a in figure, a 



small strip of soft 



iron, termed the " armature '' of the relay, placed close to the ends of the core of the re- 
lay. This armature a is supported in its position by the upright rod, or lever, r, to 
which it is rigidly attached, and which is pivoted at its lower end. 



THE MORSE TELEGRAPH SYSTEM. 53 

The jcre, the insulated coil of wire, and the armature, with the contact points G 
en the uprio'hs rod r, compose the Morse relay. 

The function of the battery is to provide the electromotive force of the circuit; that 
of the key is to open and close the circuit, thereby "stopping" and "starting" the 
flow of current in that circuit; the function of the relay is to attract and release its 
armature as the current flows or ceases to flow in the insulated wire surrounding its 
core. 

In practice the core of the relay is generally formed in the shape of the letter u, 
or a horse shoe, and two coils of wire are used, one on each " leg " of the magnet, 
which coils are joined together, forming practically one coil. 

The wire from the earth at x, Fig. 34, through the battery b, to the coils of the 
relay k, and thence via the wire to the earth at the distant station y, forms the main 
circuit. The wire between the two stations is termed the line wire, or main -line. 

The retractile springs x of the relays must be so arranged that when the core 
becomes demagnetized they shall pull the armature lever sharply against its back 
stop. The pull of the spring must be so regulated as not to exceed in strength the at- 
tractive power of the cores when magnetized. The work of thus arranging the spring 
is termed "adjusting " the relay. 

According as the current flows or ceases to flow in the circuit, and the core of the 
relay is, consequently, magnetized or demagnetized, the armatures a, a, are alter- 
nately attracted towards, or withdrawn from their cores by the retractile springs x, 

X. 

An additional circuit is shown at x and y. It includes the coils of a " sounder; " 
a small battery, b^, of one or two cells, and the supporting rod r of the relay's arma- 
ture A, and the relay contact points. This is termed a " local '' circuit. The sounder 
is termed a "local" sounder, the battery b^ a "local" battery. 

The sounder is made on exactly the same general principles as the relay, but the 
wire with which it is wound is larger, and its armature and lever are heavier. The 
armature of the sounder is also attracted by the magnetism of its core, and withdrawn 
by its retractile spring when the core is demagnetized; the magnetizing and demag- 
netizing of that core being caused by the opening and closing of the local circuit at 
the contact point c of the armature lever r of the relay as the latter is alternately at- 
tracted and withdrawn from its core by the closing and opening of the main line ; the 
lever of the relay, in this case, acting the part in the local circuit of the keys in the 
line circuit. Consequently, it is plain, that as the main line is opened and closed, the 
local circuit will be opened and closed at the same time. 

The motion of the lever of the sounder, thus produced, causes the well-known click- 
ing sound of the Morse system, and these sounds are converted into intelligible signals 
by the use of what is known as the Morse alphabet, which consists of long and short 
sounds, that are symbolized on paper as dots and dashes, a certain number of dots and 
dashes, or a certain combination of each being assigned to the letters of the alphabet, 
and to figures and punctuation marks, as will be shown presently. 

When the duration of the opening and closing of a key is arranged to correspond 
to the time required to form dots and dashes of the Morse alphabet, the signals thus 
formed are repeated by the sounder and recorded by the receiving operator. 



54 



AMERICAN TELEGRAPHY. 



Plainly, the number of relays and keys in the main circuit may be largely in- 
creased above those shown in Fig, 34. 

It is not uncommon, in this country, to have 30, 40 or more stations, with their 
keys and relays in one Morse circuit, and with but two main batteries, one at each end. 

In Fig 35, are shown four such stations, a, b, c, d; ad being terminal, and b 
c " intermediate," or "way." stations. The keys at b, c and d are closed, the key at a 
open, consequently, as this opens the entire circuit, all of the relays In the circuit are 
opened, or demagnetized, as indicated by the position of the armature levers, vfhich are 
against their " back stops," as the back limiting screws x are termed. 



FIG. 35. 




t=L^ 




MORSE TELEGRAPH SYSTEM— CLOSED CIRCUIT METHOD— THEORY. 

When any one of the keys in a Morse circuit is open, not one of the remaining keys 
can close the circuit, and when any key is operated, all the relays on the line, if they be 
adjusted, will be simultaneously operated, by reason of the alternate cessation and flow 
of the current, which alternately magnetizes or permits the demagnetization of their 
cores. 

Since then but one key may be satisfactorily operated at one time on a Morse cir- 
cuit, such as is shown in Fig's. 34 and 35, and which is termed a "single" circuit, to 
distinguish it from "multiplex" circuits, it is evident that this system is only capable of 
permitting the transmission or reception of one message over the circuit at one time. 

The foregoing arrangement of circuits of the Morse system is termed the *' closed 
circuit " arrangement, from the fact that the circuit is normally closed with ''current " on 
the line. 

The morse " open circuit " method. — ^In Europe the Morse circuits are gener- 
ally operated on what is termed the " open circuit " plan. This consists, essentially, of 
so arranging the apparatus that the battery shall only be placed to the line when a mes- 
sage is to be transmitted; at other times it is open. The arrangement is outlined 
in Fig. 2>^. AC may represent two terminal stations, and b an intermediate, or way 
station. At rest, it is seen, the batteries b at each station will be open ; while at such 
times the relays e are in the circuit. A main battery is thus necessary at each station 
— way stations included — whereas, in the " closed circuit " system employed in Ameri- 
ca, main batteries are only required at the terminal stations. 



THE MORSE TELEGRAPH SYSTEM. 



55 



An advantage of the open circuit plan is that when not in use, the battery is not 
required to supply current to the line; another advantage is that the resistance of the 
relay is not always in the circuit, since the closing of a key ''cuts" out the relay. 

The relays are provided with local sounders or registers. In some cases a " tell- 
tale " galvanometer g, is placed in the main line at each station to indicate to the ope- 
rator the condition of his transmitted signals, etc. 

FIG 36. 



£ 


1 








1 




4 r^ 


r 

T 











^ „ 




J, 

^1 


II ^f- 






e>v\vvw«^ 


HP 


T 










MORSE TELEGRAPH SYSTEM— OPEN CIRCUIT. 



TELEGRAPH CODES. 

The Morse telegraph code, which is in use exclusively on overhead lines in the 
United States and Canada, and modifications of which are in use in Europe and else- 
where is composed of dots, dashes and spaces. 

These are formed by the length of time during which the key, or other transmit- 
ting instrument, may be held closed or open, the time of making a dot being taken 
as I. 

Some of the letters of the Morse alphabet are composed of dots, others of dashes, 
others again of dots and dashes, while others yet are composed of dots with spaces be- 
tween. The latter are termed " spaced " letters. 

In length, or duration, one dash is theoretically equal to three dots. The dots and 
dashes are separated by intervals of time. The space between the elements of a letter 
is equal to one dot ; the space between letters of a word to 3 dots ; the space between 
words to 6 dots; the interval in *' spaced " letters is equal to 3 dots. 

The code in use in Europe and other foreign countries is known as the Continental 
code. 

The Bain alphabet or code was at one time in use in parts of Europe and this 
country in connection with the Bain chemical telegraph system, but is not in use at the 
present time. 

The Morse, Continental and Bain codes are given belovr ; also the Phillips code for 
punctuations, etc. ; the latter of which is now much used in "press" work throughout 
the United States. 



55 AMERICAN TELEGRAPHY. 

TELEGRAPH CODES. 

Letters Morse. Continental. Bain. 

E - - - 

H . — - 

P 

R . .. 

S --. ... 

V 

w 

X 

& . --- 

Numerals. 

Morse. Continental. Bain. 

3 

4 

6 



TELEGRAPH CODES. 



57 



Morse. 



7 — 

8 — 



9 



Continental. 



Bain. 



Punctuations, Etc. 



Morse. 



Continental. 



Phillips, 



Period 
: Colon — 

: — Colon dash 
; Semi colon 
, Comma 
? Interrogation — 
! Exclamation — 
Fraction line 
—Dash 
- Hyphen 
' Apostrophe 
^ Pound Sterling 
/ Shilling mark 
$ Dollars 
d Pence 

Capitalized letter 
Colon \ 

: ** followed by > 
Quotation. ) 
c cents 

. Decimal point 
^ Paragraph — 

ItaHcs or ) 
Underline ) 
( ) Parenthesis 
[ ] Brackets 
** " Quotation marks 
Quotation within ) 
a Quotation \ 



SOME ABBREVIATIONS IN COINIMON USE. 
{Sce^ also Military TelegrapVi Signaling.) 



57^ 



AMERICAN TELEGRAPHY. 



Mill.— Minute. 


Bn.— Been. 


Msgr. — Messenger. 


Bat.— Battery. 


Msk. — Mistake. 


Bbl. -Barrel. 


No. — Number. 


Col. -Collect. 


Ntg. — Nothing. 


Ck.— Check. 


N M. — No more. 


Co. — Company. 


K.— All right. 


L> H.-Free. 


Ots.— Office. 


Ex.— Express. 


Op r.— Operator. 


Frt.— Freight. 


Sig— Signature. 


Fr. — From. 


Fd.-Paid. 


G A. — Go ahead. 


Qk.— Quick. 


P. 0.— Post Office 


G. B. A.— Give better address. 


R R.— Repeat. 



STENO TELEGRAPHY. 



The necessity for promptness in getting new§ by telegraph into the newspaper of- 
fices before the time of going to press has long been recognized by all concerned. 

To secure such promptness Mr. W. P. Phillips has devised a system of steno- 
telegraphy in connection with an ink recorder, which has been found of much utility. 
This system, or code, is a "short hand" method, arranged for telegraphic pur- 
poses. The Morse alphabet is employed to represent the sounds used. The code 
proper consists of single letters, double letters £ nd contractions of words which rep- 
resent, arbitrarily, figures, words and phrases. Examples of the use of single, and 
double letters and contractions are given below: 
Single letters : — ■ 
B; be. 
C; see 

D; in the, 07% pence. 
F; of the. 
G; from the. 
K; out of the. 
Z ; from which. 
Double letters: 

Ac; and company. 
Ad; adopted. 
Cj; coroner's jury. 
Em; embarrass. 
Fb; of thebUl. 
Contractions : 

Abmn; abomination. 

Agum; argument. 

Ahr ; add house regular. 1 



STENO TELEGRAPHY. ^ -^ 

Such words and phrases as occur most frequently are represented by the single and 
double letters. For market quotations the first letters of the words of frequently re- 
curring phrases are used as one word. For instance: — 
Abnqh; active but not quotably higher. 
Aobfwos; absence of business for want of stock. 
Cqas; closed quiet and steady. 

In the ''reporting" code such words as are most frequently used in congressional 
debates are given preference. 

The Phillips code contains several thousand characters, or signals, each of which 
iej^resents one or more words, all of which should be memorized by the operatorbe- 
fore he can use the system to its full advantage, but even by the aid of the single, 
double and three letter contractions the ordinary speed of transmission may be much 
increased. 

As it would not be possible for an operator to receive and 'transcribe in full, as 
quickly as received, matter transmitted by this code, an ink recorder, somewhat an- 
alogous to the " Wheatstone " ink recorder, is used by which to record the signals- 
The signals thus received are then written out by two or more operators. 

Since the foregoing was written it has become customary to record this matter 
without the aid of an ink recorder, by means of the typewriter in the hands of skill- 
ful operators. 

Some Practical Notes to Beginners on Sen^dikg and ReceivinCt by the 

Morse Code. 

It is assumed that the student has thoroughly familiarized himself with the 
characters of the Morse Code. This is best done, perhaps, by separating from the 
rest of the alphabet, first, all of the '^dot" letters— thus: E-, i--, s---, 

H...., p , 6....... afterwards, the letters and- figures containing 

dashes only — thus : t — , M , 5 — — —^ , and L, long dash, , 

Cipher, extra long dash, ; and so on. 

After the alphabet, figures, and punctuations have been completely mastered, or 
even before, the student may begin the practice of making the letters by means of 
the Morse key. In connection with this subject it may be said that while the exact 
manner of holding the key and the style of sending will vary more or less with 
each individual sender, still' it is without doubt the case that much may be done bv 
care at the beginning, in the matter of acquiring an easy, fluent, and correct style. 

In words containing two or more spaced letters, space just enough, not so much 
as between letters. Still, do not underspace them. Avoid, for instance, making- 
*'meet her," "mother/' or vice versa. The letter l should be long enough to dis- 
tinguish it fairly from a dash. A double L, in such words as " skill," should not be 
transmitted as though it were '^skim,^' and "skim" should not be sent as if it were 
" skill." The letter j is made as nearly as it may be explained verbally, like tf run 
closely together ; the letter k like ta run together ; the figure 9 like TU. 

Each dot and dash should be firmly made, and always with the same degree of 
pressure, not changing from light to heavy pressure, or the reverse. On long lines 
the difference between senders is very marked. Light sending can be adjusted for, 



57^ AMERICAN TELEGRAPHY. 

somewhat, on single lines, but not so readily on duplex or quadruplex circuits. On 
long lines where there are several repeaters (see Automatic Repeaters) in circuit, 
skillful senders adopt a style which carries the signals through firmly and clearly. 
This is done by slightly lengthening the dots and dashes, and also by firmness and 
uniformity of contact at the key. 

Avoid the habit of making p for H, or 6 for p, or of making seven or eight dots 
for the figure 6, a habit which it is said is more common of late than was formerly the 
case. This habit usually arises from carelessness in learning. In making these letters 
and figures it will be well to count them mentally as made until practice enables the 
student to make them accurately automatically. 

The manner of holding the key in sending which is adopted by many of the best 
and speediest senders in this country is known as the Catlin method. According to 
that gentleman (Mr. Fred. Catlin), the key should not be held tightly. The end of 
the index finger should rest on the edge of the knob, using the thumb and second 
finger for steadying. The fingers should be arched and pliable, not straight or rigid. 
"The wrist and forearm should do the work, the finger tips and thumb being used 
as the end of the lever." The key should be so placed as to allow the elbow to rest 
easily on the table or desk. The degree of tension on the spring of the key will 
vary with the sender. Some of the speediest senders use a very stiff spring. 

It is only by constant practice that the ability to receive the Morse characters by 
sound can be acquired. The student must either have some one to send to him, or he 
must listen to the Morse passing .on some wire to which he has access. Very often the 
speed on such a wire will be too great for the student. In this case he must wait for 
slower sending. The ability to read Morse is acquired gradually, like a foreign 
language. First a letter is occasionally recognized. Then some word such as " you " 
will be caught by the ear. At other times a succession of words will be heard by the 
listener. It also sometimes happens when a ' ' clear " sender is transmitting Morse 
over the wire that the student is delighted to find that he can read much of what is 
passing. Again, a *' blind " sender will have possession of the wire and the student 
will fail to catch a word. Discouragement follows. This is, however, no good 
reason for discouragement. The time will ultimately come when the one-time student 
will be able to read all styles of sending. 

It is obvious that it is at first a difficult matter to exercise one's faculties 
to the utmost in the act of translating the Morse characters into the characters 
of the more familiar English alphabet, and at the same time give much attention 
to the style of one's penmanship, in recording the translation. So long, however, as 
the use of the pen is permitted in telegraph offices (and the typewriter has not yet 
completely superseded that method of recording messages) great care should be exer- 
cised in acquiring a clear and legible style of penmanship, while writing at a high rate 
of speed. Ornate penmanship, although not to be belittled in the telegraph operator, 
is not an essential, but plain writing is very essential. Each letter should be 
accurately written, and the letters which, like fine^ fire^ five, in long-hand, are liable 
to be confused, should be very legibly written ; even where words are not liable to be 
confused they may often be ^' blind," as it is termed, if each letter is not clearly 
defined. 



TELEGRAPHY. 5 /a 

By acquiring a habit of legibly forming each letter in the act of receiving by 
Morse, the operator will find that he will nsually write far more clearly when re- 
ceivino- Morse than when writing at his own dictation, so to speak. This has been 
the experience of many operators. 

When the sense of a message as transmitted is obscure, and the receiving 
operator has doubts as to a word, it is better to break and have the word or words re- 
peated, than to risk possible subsequent chagrin or loss. If there is doubt as to a 
word after the sender has passed it for some time, the receiver may inquire at end of 
the message or even later, "Is that chignon ?^^ indicating the message referred to, 
or simplv '^Chignon?'' To which the sender may reply "ok," or by proceeding 
without comment let silence give assent. If the word thus repeated is inaccurate the 
sender will correct it. On the other hand, an intelligent receiver by the use of good 
judgment may often prevent an error by questioning a word as received. For ex- 
ample, if the following is received: " Your fine horses leave to-night," the receiver 
should inquire " Fine, not five V In many cases of this kind the sender on thus 
having his attention particularly called to the word will say, '^Please make it five." 
If not, it will be well for the receiver to make some private mark on the message, or, 
at least, a mental note of the matter for future reference. For, in such an instance 
as the above, unless the receiver can prove his own accuracy, it may be considered a 
case of divided responsibility between the sender and receiver. But in addition to 
that, and at least equally important, a diminution of errors as a whole is thus brought 
about, and hence added prestige to the employer, for it is the company, after all, 
that the public which supports the telegraph service denounces or looks to for redress 
if errors are committed. It may indeed be pointed out that one of the important 
advantages of the Morse system over any automatic system is that the receiver is as- 
sumed to act as a check upon the sender in the matter of errors. 

In the actual work of transmitting telegrams by the Morse method, the operator 
is required to 'Hime " each message as it is sent. This is usually done with a pencil 
in the left hand while the right is engaged in transmitting the message. The 
ability to perform this double function is soon acquired by practice. The sender is 
also required to attach his allotted " initial '' or "sign," as it is termed in shop 
phrase, to the message. This timing and signing are usually done on the back of 
the message. The number of each message as sent on a given Avire or to a given 
office is also placed on the message by the sender, but on the face of the blank. 
Number sheets are generally placed on each desk with numerals placed in vertical rows. 
In large offices each operator is expected to mark off on this sheet the numbers 
corresponding to the messages transmitted or received, and to place his "sign" 
opposite the numbers thus marked off. 

In receiving telegrams the operator is expected to place the initial of the sender, 
his own initial, and the hour of receipt of the dispatch on the spaces provided 
therefor on the receiving blanks. 



CHAPTER V. 
MORSE TELEGKAPH APPARATUS, ETC 



MORSE TELEGRAPH KEYS. 

The function of the Morse telegraph key is to open and close, or "make'* and 
*' break ' ' the circuit, as already stated. 

That the Morse key is one of the most important instruments in the telegraph service is 
c fact which has frequently been recognized by the officials of the principal telegraph 
c (impanies of this country, and the wishes of the operators in respect to the form of key 
desired, have generally been consulted, even to the extent of displacing keys already 
extensively in service. The wisdom of such action is evident when it is considered that, 
at a low estimate, an operator will transmit with the same eif ort from 5 to i o more 
messages per hour with a key suitable to his style than with one not so suitable. 



FIG. 37. 




OLD STYLE MORSE KEY AND CONNECTIONS, 



The tendency of the Morse telegraph key in this country has been from that of a 
heavy, cumbersome mass of brass, as outlined in Fig. 37, which represents a style of 
key in vogue twenty-five years ago, to those shown in Figures :^S, 39, 40; weighing 
about 7 J ounces, each. 5^ 



MORSE TELEGRAPH KEYS. 



39 



The construction of the modern telegraph key may be readily understood from 
Fig. 38. In that figure, l and l^ are metal extensions, termed " legs/' projecting from 
sm oval-shaped metal strip, or base. The leg l^ is connected directly with the base. 
The leg l passes through the base, and is insulated from it by a bushing of hard rubber. 
On its top it is furnished with a cone-shaped cap c, termed the anvil, carrying a small 
platinum point. A small flat strip of metal, s, extends out a short distance from the 
cap. At a point on its under side, directly above the platinum point on c, the lever 
is also supplied with a projecting platinum point termed the hammer. The lever a of the 
key is supported at its trunnion by the set screws shown. A curved strip of metal, 

FIG 38. 




"BUNNELL" KEY. 

M, tci\yQed the "circuit closer," is pivoted on the base, as shown. The lever a, and 
the circuit closer m, are each supplied with hard-rubber finger-tips, or knobs, by which 
they laay be freely moved. A spring, adjustable by the set screw f, normally lifts 
the lever a from the contact point c. One terminal of the circuit, of which the key 
may form a part, is brought to leg l, the other teminal to leg l^. As the leg l is in- 
sulated from the base, the circuit would be open at c but that the circuit closer m slips 
between s and the base, thereby continuing the circuit from the oval to leg l. 

When the operator is about to " send," the circuit closer must first be pushed out 
from s, so as to permit the lever a, when it is operated, to open and close the circuit. 

Platinum contact points are employed because of the fact that, at each time an ordi- 
nary telegraph circuit is opened, a small spark occurs at the point of opening (see self- 
induction); the result being that if a metal, such as brass, were used, the surface 
would sooTi become oxidized^ and, measurably, non-conducting. The points could be 
filed and thus temporarily made conducting, but at the cost of rapidly wearing the 
metal, etc. Platinum, being virtually non-oxidizable, is not affected in this way and 
fmther, its hardness renders it much more durable than a softer metal would be. 

When tiie key, shown in Fig. 37, was first employed, it was not furnished with a 
circuit closer, but a special circuit closer, much resembling an old fashioned window 
catch, svas used separately for that purpose, namely, to short-circuit the contact points 
of the key when the latter was not in use. This arrangement is also shown in F'ig. 3 7, 
C beinj; ihe circuit closer, the knobic of which was puslied to the right in siMidiug. 



6o 



AMERICAN TELEGRAPHY- 



Keys, almost as large as those introduced by Morse, are at the present day in use 
in the British Postal Telegraph service. The operators in that service have frequently 
expressed the opinion that they can " send " as speedily and witij as little fatigue as the 
users of the lighter keys in this country. 



FiG. 41. 




• BUNNELL " LEGLESS KEY. 

The Style of key show^ in Fig. 38, is known as the '• Bunnell " key. It may be 
said to have been the pioneer of the many light, " solid lever" keys now in service in 
this country. Fig. 39 illustrates the " Steiner" key. Fig. 40 the " Victor" key. 

The keys shown in Fig's. 38, 39 and 40, are known as '' leg" keys. That in Fig, 
41 as a '' legless " key. 

FIG. 39. 




"STEINER" KEY. 



Leg keys are held to the table, or desk by the pressure of the set screws against the 
under part of the table, the set screws also holding fast the ware terminals. It is under- 
stood that suitable holes are bored in the desk for the passage of the key legs. The 
legless key is screwed fast to the desk, while the line wire terminals are attached to the 



SELF-CLOSING KEYS. 



6i 



key by means of the binding screws provided on the base of the key. 

Self-c LOSING "keys. — Every one connected with telegraphy knows the vexation 
caused and time lost by the faihire to close the keys. To avoid delays, etc., arising 
from this failure, many attempts have been made to devise a " self-closing key " which 
would be satisfactory in all respects, but apparently none such has yet been found 
least none has been adopted for general use. 



at 



FIG. 40. 




"victor" key. 

Whether this is due to inherent lack of merit in the devices or to a lack 
of desire on the part of the telegraph companies to encourage negligence on the j^art 
of employes is, perhaps, debatable. It is, however, unquestionable that some of the 
self-closing £ rrangements devised would provide a "remedy" which would be rather 
worse than the complaint; as, for example, that one in which the operator's elbow, 
while he was sending, was to be caused to open a circuit closer which would be au- 
tomatically closed when the elbow was removed. 

Fig. 42 will illustrate the principle of one form of self-closing key which, after 
a brief trial, has seemingly fallen into disuse, and it is not known that any substitute 

FIG. 42. 




SELF CLOSING KEY. 



has taken Its place. The key resembles other modern Morse keys quite closely. Its 
peculiarity is that the finger-tip of hard-rubber is in two parts, a, b, one within the 
other. In size, a is about the same as the finger-tip of the ordinary key. At its cen- 
tre a circular hole is cut, into which the smaller part b, loosely fits, b rests on a 
metal pin m, into whose lower end a pin, resembling a small, inverted screw, is in> 



62 



AMERICAN TELEGRAPHY. 



serted. A small, sj^iral spring, resting on an insulated cross-piece, c, gives m and, 
with it B, an upward tendency. When pressed upwards, the flange f of the inverted 
screw, makes contact with the metal of the lever. The tip a is suitably sup- 
ported by the metal of the lever. The spiral spring below f, normally, raises the 
hard-rubber tip b slightly above a. 

It will be seen that the inverted screw is electrically connected by a wire with 
the contact p, of the key. Thus, when the key is " open," the circuit is closed, at the 
key, via that wire, and the inverted screw below, :si, is insulated from all other parts 
of the key lever, except at the flange. When the operator uses the key he places a 
finger on b, pressing its surface level with that of a. That action opens the circuit at 
the flange. When he further depresses the two discs and the lever, he closes the cir- 
cuit at p. Care is necessary to remember to keep disc b level with a during sending. 
As soon, of course, as the operator removes his hand from the key, the spiral spring 
of M automatically closes the circuit. The act of depressing the tip b to a level with 
A, is equivalent to " opening" the key in the usual way. 

Another suggestion in this direction was that the circuit closer of all keys should 
be removed; that the contact be made on the back instead of the front of the key, 
and that all the relay armature lever contacts be placed on the back stop, as, theoretically, 
shown in Fig. 43. This arrangement would give the signals on the front stroke. It 

FIG. 43. 



X 



i 



Zl^rze/ 



^ 



(H 



] 



-^ 



y '\ y r\ f\ f\ !\ f\ 






/f 



\ 



would also, besides insuring a remedy for " open " key delays, of the usual order, put the 
local batteries of the sounders on "open circuit," except when in operation. The dis- 
advantage would be that the transmitted signals would probably suffer, owing to un- 
certain action of the spring of the key, upon which spring the actual making of the 
contacts would chiefly depend. 



MAIN LINE RELAY 



THE MORSE RELAY. 



63 



The Morse relay has also undergone many changes as to its shape, dimensions and 
resistance, since it was first invented. As stated in the introduction, it was thought 
that a remarkable advance was made when a relay, weighing only 70 or 80 jwunds 
was produced. The Morse relay of to-day weighs but littls over 3 pounds. As late as 
1867, relays wound to 1,100 ohms, were employed in this country in regular telegraph 
service. 

Main Li:ne Relays.— Specimens of Morse relays, now in general use on main 
lines in this country, are shown in Fig's. 44 and 45. These only differ as to details 
For example, in Fig. 44, the armature is a part of the lever, while in Fig. 45 the arma- 
ture is a separate 23iece of soft iron, carried by a brass or nickel-j^lated lever. Main 
line relays are, as a rule, now wound to 150 ohms resistance. 

These relays may be "adjusted" in two ways; either by drawing the cores 
away from the armature by means of the adjusting screw, a, which is attached to the 
cores suitably for that purpose, or by the aid of the retractile spring e, attached to the 
annature. In wet weather, when, owing to '' escapes " due to defective insulation, 
the cm-rent strength is much increased a't the battery end, or ends, of the wire, the re- 
lay is best adjusted by withdrawing the coils, or cores from the armature, until the lat- 
ter works freely. (The spring should not be adjusted more than to give the armature 



FIG. 44. 




MORSE MAIN LINE RELAY. 



prompt action. Thousands of retractile springs are wasted annually by turning them 
around the cross-bar of the winding screw s.) The explanation of the increased 
strength of current, at such times, is that the circuit is virtually shortened, and, con- 
sequently, the resistance offered to the battery is decreased. The actual resistance 
of the line wire itself, of course, remains the same. {See remarks in connection with 
Delaney line adjustment device.) 

In Pig's. 44 and 45, the winding screw s is movable to or from the relay coils hr 
aid of the "upright " t, through which the support .1^ of that screw passes. Tlie si-ivw 



64 



AMERICAN TELEGRAPHY. 



posts B, b1 are for the local connections, and posts ^ ^' are for the main line connections. 
The dotted lines show the manner of connecting under the base-board of the relay. 
As the object of the relay is merely to ''• relay," or " repeat " the signals passing over 
,the main line to the "sounder" the play of its armature should not be large. This 
play is regulated by moving forward or backward the contact screw on the front stop 
(that is the screw next the coils), and the screw on the back stop. The " armature " proper 
consists of the strip of soft iron opposite the cores, but, generally speaking, among opera- 
tors the lever which carries the armature, is included in that term. The armature 

FIG. 45. 




MORSE MAIN LINE RELAY. 

lever is pivoted as shown. Care should be observed that the screws do not bind the 
movement of the lever. The armature and its supports are all insulated from the brass 
sockets, or '' spectacles " into which the coils of the relay fit, as shown. 

Pocket Relay — ^This relay is designed for use in line testing, as, for instance, 
when a break may huve occurred on several wires, and the foreman is taking orders or 
giving them, etc. It is placed directly in the main line. The pattern of pocket relay, 
shown in Fig. 46, is about 6 inches long by 3 inches wide, and 2\ inches deep. Screw 
posts are provided at the left end for the line wires. The construction of the armature 



FIG. 46. 




POCKET RELAY. 

?!B^ lever of this instrument is such as to produce a very fair sound. 

Poxy Relays. — This is a name given to a relay which differs from the main line 
relay only in minor details of construction, and in the resistance, or winding of its coils. 



THE BOX RELAY. 



65 



which varies from about 20 to 100 ohms. It is mostly used on "private" lines. For 
lines up to 15 miles in length the " pony " is " wound" up to about 20 ohms. For lines 
20 to 40 miles, about 45 ohms. For lines 70 to 75 miles, about 75 ohms. A specimen 
of a pony relay is shown in Fig. 47. 



FIG. 47. 




PONY RELAY. 



The Box Relay. — This is an ordinary Morse relay, the coils of which are cov- 
ered by a square, or oblong, wooden box, as seen in Fig. 48. Holes are cut in the left 
end of the box opposite the front contact point of the amature lever, and opposite the 
ends of the cores of the relays, and at the right end of the box for the adjusting screw 
of the coils. The instrument is adjusted in the same manner as the unboxed relay. 
The box relay is generally provided with a Morse key on the base-board. 

FIG. 48. 




BOX RELAY. 



This form of relay is mostly used by linemen, or others, in testing, or for temporary 
offices when a local battery is not to be had, or may not be desirable. The box over 
the coils acts as a sounding board, and increases the sound of the signals to such an ex- 
tent as to make them clearly perceptible without the aid of a sounder, but a sounder 
may be connected in, if desired. The box relay, shown in the figure, is technically 
known as a " box relay with key on base." 



66 



AMERICAN TELEGRAPHY. 



SOUNDERS. 

The object in using the " sounder;"' in Morse telegraphy is to obtain an increased 
sound as compared with that given out by the Morse relay. 

The necessity for the sounder in Morse telegraphy in addition to the relay is 
primarily due to the fact that the strength of current with a given electromotive force 
is proportional to the resistance of the conductor; the strength of current decreasing 
as the resistance increases. As the resistance of a wire of a given diameter increases 
directly with its length, the longer the wire, the weaker will be the current. 

The magnetism developed in a given electro-magnet, such as a relay, or sounder, in- 
creases with the strength of current in the coils, and also with the number of convolu- 
tions of wire in the coils ; the resulting magnetism, being, within certain limits, directly 
proportional to the product of the strength of current multiplied by the convolutions 
or turns of wire. This product is termed the " ampere turns."* 



FIG. 49. 




THE "BUNNELL' SOUNDER 



An instrument to produce sounds loud enough to be easily heard by the operator, 
requires that the apparatus should possess considerable mass, and iis its moving parts 
require to be actuated quickly and without lag, the use of a strong retractile spring is 
entailed. This necessitates the use of a magnet of considerable strength. 



It is found that, to produce the clear, loud " ^lick " 
about one quarter of an ampere is needed in its coils, 
volutions of the sounder to be, say, 900, the " ampere 



of the ordinary Morse sounder, 
Assuming the number of con- 
turns " of the sounder will be 



225. Consequently, it may be said that 225 ^^-impere turns ^' are necessary to 



* The limit referred to is when what is termed the point of magnetic saturation of the iron is reached. This statement 
«hnnld ho Tver be miaiified After this point is reached the magnetism increases directly with the magnetomotive force, 
but life linr/offorce^i^i the circlet do not thereafter increase in the same ratio as before saturation. Saturation is how 
eSrrareW reached in tl^e magnets used in telegraphy. Hence it may be assumed here tha the magnetism developed wu 
be nroDortlonal to th^^ A hypothesis due to Ampere and amplitied by ^^eber to explain the 

effcS fXuiSa ?he hitrodu of iron into a magnetic circuit, and to account for saturation of the iron is. that each 

nKilecule S the" iron i^^^^^^ the normal state each acts mdependently of its neighbor: the result 

be nc^ l^ltone neutial z^ and no magnetisii is apparent. When, however, an external magnetomotive fo.je. due 

foJ ilstuice t^a "urrent in a coil of wire, is brought to bear upon the iron, more or less of its molecules are turned so th^.t 
?eii ifnel of forcfare add^^ circuit. When the external magnetomotive forci^ is such that all the ^"olecular lines of 

force of the iron are brouc^ht into play, the saturation point of the iron is assumed to be reached. In a soleno d. that is. a C( il 
Swle without ron, the ^suiting lines of force or magnetic flux are proportional to the ampere-turns without limit. See p. 36. 



SOUNDERS. 07 

properly oj^erate an instrument capable of furnishing tlie "sound " required for success- 
ful Morse telegraphy. 

If a Morse sounder were placed directly in a line wire extending from, say, New 
York to Philadelphia, and having a resistance, including the internal resistance of the 
battery, of, say, 1200 ohms, which would, with a battery of 100 cells, give a current of 
about .c8 ampere, (80 milliamperes) the "ampere turns " of the sounder would be 72, 
which is much short of the amount necessary. To secure the desired " ampere turns " a 
battery of, at least, 600 cells of " gravity " would be required on such a circuit. It is, 
therefore, evident, if for no other reason than the foregoing, that it would beunadvisable 
to attempt to supply sufficient current to operate an instrument such as an ordinary 
sounder on long telegraph lines. It is found more economical to employ a main line 
relay having a much larger number of convolutions, and a light armature, not designed 
to produce a large volume of sound, and then to cause this relay to operate a sounder 
by means of a local battery. 

In fig's. 49, 50 and 51 are shown styles of sounders now in use in this country. 
The first is known as the "Bunnell" sounder: the second as the "West- 



FIG. 50. 




THE " WESTERN ELECTRIC " SOUNDER. 



ern Electric " sounder. One point of difference between these sounders is that fig. 49 
is supplied with a spiral spring s; that in fig. 50, with a retractile spring. Fig. 51, 
represents the " Victor " sounder. In this the trunnion of the lever rests on pins, or 
points, instead of the usual bearings. The. pins project from above the coils near the 
right end of the armature lever, but are not seen in the figure. The usual resistance of a 
^' local " sounder is between 4 and 5 ohms. 

Main line sounders. Main line sounders are used on main lines when, for any 
reason, it is not desirable to have relays in the circuit. The resistances of these 
sounders is about 20 ohms. In other respects they resemble the ordinary sounder. 



68 AMERICAN TELEGRAPHY. 

While the additional convolutions on the main line sounders add considerably to 
the total resistance of a line wire, already moderately large, yet the added resistance 
reduces the total strengtli of current but slightly, and, on the other hand, the increased 
number of convolutions, as compared Avitli the ordinary local sounder of 4 ohms, 

FIG. 51. 



"VICTOR ' SOUNDER. 

augments the ampere turns, and, consequently the magnetism, of the magnet in 
greater proportion than the strength of current is reduced by the added resistance of 
the coils. An illustration of this will perhaps be useful. 

Assuming a local circuit of 2 cells and i local sounder, the total resistance of 
the circuit will be: — 

2 cells, 2 ohms internal resistance each, 4 ohms. 

I sounder, 4 ohms, - - _4 ^ 

Total resistance of circuit, - 8 ohms. 
The resistance of the connecting battery wires may be neglected. 
Electromotive force, 2 volts, divided by the resistance, 8 ohms, gives a current 
strength of .25 ampere. Ampere turns = .25 X 900 = 225. 

Assuming now it is desired to operate 4, 4-ohm sounders on a short wire having 
a resistance of, say, 100 ohms. If w^e increase the battery to, say, 30 cells, we have: 
Internal resistance, 30 cells, - - - 60 ohms. 

Resistance of 4, 4-ohm sounders, - - - 16 " 
Resistance of line wire, - - - - 100 " 



Total resistance, ... - 176 ohms. 
And a consequent strength of current of -^yf^ = -17 ampere; giving 153 ampere 
turns, which is considerably less than required to operate the 4 ohm sounder satis- 
factorily — namely, as we saw, 225. 



SOUNDERS. 69 

If now we substitute for tlie 4 ohm sounders, four 20-ohrji sounders, we have: 
Internal resistance of 30 cells, - - - 60 ohms. 

Resistance of 4, 20-ohm sounders, - - 80 " 

Resistance of line wire, - . _ . 100 " 



Total resistance, - - - - 240 ohms. 

Which gives a strengtii of current of 2^^ = -^^S arnpere. As the number of con- 
volutions of tlie main line sounder is about 1800, we thus obtain 225 ampere turns. In 
other words, the current strength of tlie circuit is reduced from .170 to .125 amj^eres, 
by the additional 64 ohms of the main line sounders, but tlie magnetic strength of 
those sounders is increased, by the additional convolutions, to a point virtually equal 
to that of the 4 4-ohni sounder in a local circuit. 

The foregoing figures, relative to the*number of convolutions, are approximately 
correct The exact windings of sounders and relays as furnished by the manu- 
facturers are as follows : 

150 ohm Morse relay, 30 layers of No. 30, B & S wire on each core; 144 con- 
volutions to each layer; 8640 turns in all. [Sfd \\ ire Gauges.) 

4 ohm sounder, 10 layers of No. 24, B & S wire on each core; 47 convolutions to 
each layer; 940 turns in all. 

20 ohm sounder, 14 layers of No. 25 ; B tfe S wire on each core, 67 convolutions to each 
layer; 1876 turns in all. 

In every case silk covered wire is now used in the coils of these instruments — 
relays and sounders. 

Amount of current that is required for proper operation of 150 ohm Morse 
relay, about 40 milliamperes; for polarized relays on duplex and quadruplex circuits, 
about 25 milliamperes; for quadruplex neutral relays, about 70 milliamperes, depend- 
ing on the ratio with transmit' er open and closed {see page 207). The amount of 
current required to operate the Brown and Allen relay is about 7 milliamperes. A 
sensitive polarized relay on cable circuits of moderate length will work with 15 
milliamperes. 



THE MORSE REGISTER. 

The Morse embossing "register " which was in extensive and almost exclusive use 
as a " receiver " in the operation of the Morse telegraph system, until the present 
method of receiving by sound was adopted, is now mainly used as a "call '' recorder 
in connection with the District Telegraph Messenger service, Fire Alarm Telegraphy, etc. 

The ordinary Morse embossing register consists of an electro-magnet, usually 
operated by the armature of a main line relay, which electro-magnet, placed in an 
oblong frame containing clock-work and a spring motor, by means of which two brass 
rollers are given a tendency to rotate. A strip of paper is passed between these rollers 
and is carried along by them when the instrument is in operation. An extension liom 



70 AMERICAN TELEGRAPHY. 

the armature lever of the electro-magnet carries a pencil which, in certain positions of 
the armature,is caused to impinge against the paper, indenting thereon long or short 
dashes, as the case may be, which indentations appear as embossings on the upper side 
of the paper strip. 

As the electro-magnet is operated by the main line relay any signals transmitted 
over that line are recorded on, and may be transcribed from, the embossed strip of 
paper. 

INK RECORDING MORSE REGISTER. 

An ink recording register is shown in Fig. 52. The manner of its operation will 
readily be perceived. A disc d and an ink-roller i are placed on the outside of the 
register. The disc is caused to revolve by clock-work gearing within the box. The 
ink-roller is held lightly against the disc by«a spring s, attached to the arm a, which 

FIG 52. 




INK RECORDING MORSE REGISTER. 



carries the roller. Thus the edge of the disc is kept wet with ink. The paper is pulled 
along by the rotation of rollers r, r^ ; R being operated also by gearing within the box. 
The armature lever of the electro-magnet em is extended to a- point just under the 
disc D. This extension of the lever em carries a flat sleeve, or guide, in the upper half 
of which a slot is cut. The paper is passed through the guide in the manner shown. 
Consequently, as the armature is operated, the paj)er is alternately lifted up against 
the disc and withdrawn from it, by which action a long or short mark is left on the 
paper according to the duration of the impact of the paper against the disc. 






THE MORSE REGISTER. 7 1 

This ink recording instrument can be used in any place where the ordinary Morse 
register is applicable, the former having the advantage that the ink record is much 
nore readily decipherable than the embossings of the Morse register. 

(For a description of a self-starting and stopping Morse register, see District 
Felegraph Service). 



AUTOMATIC PAPER WINDER. 

This is a device, Fig. 53, used in connection with printing telegraph ''tickers" or 
•egisters of any kind in which paper tape is employed. Its office is to wind up the 
)aper as fast as it h delivered from the receiving instrument. The reel is turned by 
he clock spring o. The paper is held taut by the weight-roller x, as shown in the 
igure. 




AUTOMATIC TELEGRAPH SENDER. 

It is sometimes desirable to have a simple means whereby Morse signals may be 
Lutomatically transmitted. This may be done by the Wheatstone transmitting 
ipparatus, but that api3aratus can hardly be classed as simple. 

The principle of a device which has been availed of at intervals by different ex- 
)erimenters, probably first by Edison, is illustrated in Fig. 54. At the left of the 
igure the top of an ordinary Morse " register " with an extra attachment consisting of a 
lelicately pivoted lever l, whose lower end rests easily on the paper p, are shown. The 
ipper end of the lever carries a contact point and is close to a contact point c, which is 
)art of a circuit, x, in which is included a sounder s and battery, b. The lever itself is 
Iso part of the circuit. The paper p, has previously been embossed by tlie 
tencil of a Morse register in the ordinary way. As the paper is drawn along by tlte 
oilers of the register, the embossings on its surface raise the lever l, and cause its 



7^ AMERICAN TELEGRAPHY. 

upper end to close the circuit at c, for a longer or shorter interval depending on 
whether the embossing is a dot or a dash. By a slight modification of the extra attach- 
ment the lever can be caused to reverse the polarity of the battery and thus be made 
to operate a "polarized " relay. As the motion of the lever l is necessarily limited 
a close adjustment is required at the contact points, but for moderate speed this is an 
easy matter. 

FIG. 54. 




AUTOMATIC TELEGRAPH SENDER. 



This apparatus has of late been much improved by Weiny and Phillips, and is 
now termed the Phillips-Morse automatic telegraph. In the new arrangement three 
rows of embossings are made on the transmitting paper to secure greater accuracy 
at high speeds. The claim for this device is that messages may be prepared in 
advance by operators in case of wire trouble or of an abnormal increase of business, 
and be transmitted over the wires at a speed thrice that of the best speed by hand 
sending, or, say, 120 words per minute. Being embossed as received messages may 
be copied from the register by clerks, or sent through the automatic sender and 
received by a Morse operator at any desired speed, as the speed of the machine is 
variable at will. 

TELEGRAPH TRANSMITTERS. 



With the object of securing a simple and speedier method of transmitting the 
Morse alphabet than the manual key method, Morse devised several arrangements; 
one of the first of which is shown in Fig. 55. It consisted of a plate of metal a on 
which were several pieces of metal, the length, number and arrangement of which 
corresponded to the dots and dashes of the Morse alphabet. The spaces between 
the raised pieces of metal were filled with an insulating material, flush with the 
surface of the raised metal pieces to secure an even surface on the plate. The 
battery was connected to the plate by a binding post c, and a metal pointer p, having 



TELEGRAPH TRANSMITTERS. 



1Z 



an insulated handle, was connected with the line. Consequently, when the pointer 
touched any one of the raised pieces of metal the circuit was completed. The opera- 
tor held this pointer in his hand and drew it over the surface of a desired character, 
closino-and opening the circuit as he did so in a manner to correspond to that letter. 
Anothersoraewhat similar device, also by Morse, consisted of a metal cylinder on 
the surface of which the characters of the Morse alphabet were, in a practically similar 

FIG. 55. 




way, arranged. Above each of the characters representing a letter, a key, which could 
be readily depressed by the finger, was placed. This depression brought a metallic 
brush, connected to the under side of the key, into contact with the surf ace of the cyl- 
inder. The same act of depression of a key permitted the cylinder to make a partial 
revolution. The cylinder being connected to the battery, and the metal of the key to 
the line, the foregoing actions resulted in the transmission of Morse characters. These 
devices, however, did not get into extensive use, the reasons for which were stated 
to be that the signals were not transmitted uniformly by the pointer in the hands of 
»-tie operator or by the depression of the key upon the insulated cylinder. 

The complication of machinery, also, doubtless, had some bearing on the matter, 
asm those days the bulk of business was not great. 

In explanation of the fact that these methods were not availed of to meet the 



74 



AMERICAN TELEGRAPHY. 



demands of increased business, later, it may be supposed that inasmuch as the average 
operator is able to "send" with an ordinary key, as fast as the average operator can 
receive, there was nothing to gain by increasing the speed of transmission. 

The typeweitee in telegeapht. — Within the past few years, however, the 
*' typewriter " has been adopted by many telegraph operators as a means of recordino; 
received messages, and its use for this purpose is steadily increasing in this country. 
Indeed, the ability to manipulate the typewriter expertly is now virtually essen- 
tial to employment as operator in the service of the various Press associations. Also, 
it may be added, in the Wheajtstone automatic departments of the telegraph compa- 
nies of this country the telegrams are in many cases " transprinted " from the " receiv- 
ed " slip to the regular message blank,by means of a tyj^ewriter in the hands of the 
"copyist. "It is very likely, also, that as soon as the means of adjusting the telegraph 
blanks to the typewriter has been simplified that instrument will be used generally in 
the large telegraph ofiices for recording despatches as they are received. An expert 
with the typewriter can write from 60 to 70 words per minute. It is therefore evident 
that there would be time and to spare for the insertion of " time received, " the op- 
erator's " sign " etc., even when receiving at the rate of, say, 45 or 55 words per minute. 



FIG. 56. 



Lin^ 




This use of the typewriter, with the accompanying gain of speed in transcription, has 
revived, in some quarters, the employment of means for increasing the speed of 
transmission of signals beyond that at which the ordinary operator can send, and 
this without resorting to the use of devices for especially preparing the despatch tor 



TELEGRAPH TRANSMITTERS. 



75 



transmission. One of the devices having this object in view, namely, the La Dow 
Transmitter, will be described. 

LA DOW TELEGRAPH TRANSMITTER. 

The La Dow Transmitter, which aims to overcome defects of earlier transmitters, 
is shown in side view Fig. 56. It consists of a key-board arranged on the general 
plan of that of a typewriter. One key is shown at c. Each key is pivoted at the 
right hand end, as shown at c. It is held in its normal position by spring c^ Near 
the center of each key is attached a rudder-shaped, thin piece of metal f, having por- 
tions of its lower edge insulated, as shown by the thick lines. Each of these attached 
pieces of metal tas a corresponding portion of its lower edge insulated, namely at a' 
in the figure. The rest of the edge is divided into sections corresponding to the 

FIG. 57. 




letters of the Morse alphabet. The insulated portion a'^ is directly over a metal cyl- 
inder H which extends under all of the keys, and which cylinder, when in use, is 
kept in constant rotation by a suitable spring or motor shown at the right of Fig. 5 7. 
A flat metal spring, or brush k, rests on the cylinder, and to this spring the battery 
is attached, the line being connected with all the keys at e, as shown. In Fig. 56 
the key is assumed to be depressed. This places the insulated portion a^ of r, ofi the 
cylinder, the result of which is that r, which is hinged at s, is carried to the left 
a certain distance, during which journey the metal portions of its lower edge, in turn, 
mjike contact with the cylinder, thereby completing the circuit for a period corres- 



•IP 



76 



AMERICAN TELEGRAPHY 



ponding to the lengths of the uninsulated portions. In the case of f it will be seen 
that the insulated portions, Fig. 56, are so arranged that the letter A will be trans- 
mitted. When the finger is removed from the key the spring s' immediately brings 
F back to its starting-point. In a similar way all the other keys will transmit signals 
according to the letter assigned to them. Suitable means are provided for holding 
the "rudders" in line. Although this arrangement is designed chiefly to increase 
the ordinary speed of transmission of signals, it is also intended for those who may 
have writers' cramp, or who may not be expert "senders." This transmitter is 
shown in front view in Fig. 57, in which r indicates the rudder-shaped pieces of 
metal. H is the cylinder. 

THE YETMAIs^ KEYBOARD TEAKSMITTER. 

This modification and improvement of the La Dow transmitter just described 
has been introduced into practice of recent years. By its use quite a high speed of 
transmission is obtained. The character of the signals is very good. As in the case 



FIG. 57(5. 




DOUBLE ACTION-KEY. 



of the La Dow transmitter, the mechanism of the Yetman transmitter is so arranged 
that the depression of a key transmits the complete Morse letter. In the latest type 
of the Yetman keyboard transmitter it is combined with an ordinary typewriter so 
that the one keyboard serves as a typewriter and keyboard transmitter. This trans- 
mitter has been employed successfully on some of the longest circuits in this country, 
as, for instance, the New York-New Orleans duplex circuit. 



DOUBLE-ACTION A:N'D AUTO-TRANSMITTERS. 

The desire to supply the demand for a type of key differing from the ordinary 
Morse key with its up--^nd-down motions, especially to enable operators afflicted with 



VIBROl LEX TRANSMITTER. 



76(05 



loss of " grip " or loss of ability to transmit telegrams by the vertically operated key, 
as well as to afford operators generally an opportunity to vary the monotony of ver- 
tical sending, has led to the introduction of numerous laterally operated and auto- 
matic transmitting keys, two of which are shown below. Fig. 57^ is known as the 
Bunnell double-speed key. At rest the lever is between two contacts. A movement 
of the lever to the right or left closes the circuit. It requires but one-half the mo- 
tions of the ordinary key to form a character of the Morse letters, and these motions 
are made by a sidewise rocking motion of the hand, easily acquired. Keys combin- 
ing a vertical and lateral motion of the key as desired have also been utilized. A 
key termed the " twentieth century" key employs this lateral motion. It is not a 
double-action key. Double-action keys have been tested a number of times within 
the joast thirty years, but do not appear to have attained very extensive use. 

In Fig. 57c is shown the " Vibroplex,'^ a form of ti'ansmitter which exempli- 
lies a number of more or less similar automatic transmitters, variously named the 
"auto-dot," the " mecograph," etc. The vibroplex consists of a pendulum arrange- 
ment p extending from one end of a key k. This key is pivoted at N. c, c^ are 
contact posts. L, L^ are the line posts. L^ c^ and c are insulated from the iron base 
of the key. L is in contact with the base and consequently is in contact also with the 
lever of the key k. Normally, spiral springs E K hold the lever l in a middle or 



FIG. 57^. 




VIBROPLEX TRANSMITTER. 



"open " position between the stops s s. When key k is pushed to the left by means of 
knob m it closes the circuit at the dash contact c. When the key is pushed to the 
right by means of knob m\ the pendulum is set into vibration and the circuit is opened 
and closed rapidly at the dot contact post c', contact with the lever of key K being 
made by a flexible U-shaped contact. 

In the act of sending the operator moves the key lever to the left and holds it 
there for a time corresponding to a dash. To form dots the key is moved to the 
right and is held there while the pendulum automatically transmits one, two, three, 
four, five, or six clots, as the case may be. A braking device d dampens the vibra- 
tion of the pendulum when a dash is being made. The circuit of the transmitter is 



76^ 



AMERICAN TELEGRAPHY. 



closed by means of a metal strip (corresponding to that of the Morse key), the knob t 
of which is seen in Fig. 576'. After a little practice the ability to rapidly transmit 
the characters of the Morse alphabet in this way is easily acquired. The speed of 
transmission is regulated by moving the bob b along the pendulum. It has been 
found that signals made by this transmitter carry over the longest circuits, and as 
the sending is done by an arm movement and the key is never grasped as in vertical 
sending the manual work of Morse signaling is much simplified to the operator. 

Other transmitters of this general type employ a magnet controlling the pendu- 
lum, but while the operation of these transmitters is perhaps somewhat more accurate 
than that of the natural pendulum, the added cost of the magnet and of a local bat- 
tery for its proper working appears to offset the advantage mentioned. 

These automatic transmitters may readily be placed in a desired circuit by means 
of a flat metal plug which is inserted between the contact points of the ordinary 
Morse key. Flexible insulated wires connect the plug with the binding- posts of the 
transmitter. 



In order that the noise incidental to the operation of the typewriter should not 
interfere with the reception of the Morse signals by sound, an arrangement, illus- 
trated in Fig. 57fZ, has been devised,, whereby the signals emanating from the 
sounder are much amplified, and by which the sounder may be placed in any position 



FIG. 57^. 




SOUNDER RESONATOR. 



desired by the operator. The device consists of a resonating box, suspended by an 
adjustable support, and within which the sounder is placed. The local circuit is con- 
ducted to the sounder by flexible wires shown. This arrangement, it is obvious, may also 



SWITCH BOARDS. "]'] 

be utilized to advantage in railway station offices, and in other places where confusing 
noises prevail. Another advantage gained by the adjustable feature of the support, 
apart from its use in overcoming the noise of the type-writer, is that the sounder may 
be placed so close to the ear that only the operator can hear the signals ; the sounder 
itself being adjusted down accordingly. By this means complete secrecy is obtainable, 
when desired. 

In connection with this subject, it may be noted that it has been customary for 
the attendants of quadruplex and duplex circuits, where the apparatus is " bunched '* 
on one corner of a table, etc., (in consequence of which it is next to impossible to dis- 
tinguish between the different signals, in the ordinary way), to employ a rod of wood 
of sufficient length to reacli from the instrurxients on the table to the ear of tlie at- 
tendant, for the purpose of separating the signals. By placing one end of this rod on 
the base of the proper instrument, and the other end to the ear, the signals from that 
instrument can be heard with ease, regardless of the conflicting noises. 



SWITCH BOARDS. 



MAIN OFFICE SWITCH BOAED. 



Til's nsefal piece of telegraph apparatus is shown c.iagrammatically in Fig. 58. 
\t .jonsistsJ of a large board, or series of boards, of any desired size, on the face 
of which are ai'ranged, vertically, narrow strips of brass, termed straps. On the 
back of the board are other strips of brass or copper running at right angles to the 
vertical straps. Metal discs connected with the horizontal strips at the back of the 
board, pass, through holes in the board, to the front of the board, flush with the sur- 
face of the straps. The discs on their sides nearest the straps, liave semi-circular 
notches cut in them. Similar notches are cut in the straps immediately opposite those 
in the discs. "Pin" plugs, like tliac shown in Fig. 59, with a cone-shaped metal piece 
n and an insulated handle e, are made to fit in the hole formed by the two semi-circles, 
thus metallically connecting the strap and back strip together, for a purpose which 
will be stated presently. 

A series of peculiarly shaped flat m^tal springs, termed "spring- jacks" are placed 
at the foot of the board, one spring-jack under each strap. In some cases two series 
of such spring-jacks are placed under the board, two jacks under each vertical 
strap. A board thus equipped is termed a " double spring- jack switch board with 



78 



AMERICAN TELEGRAPHY. 



Straps." The number of straps gives a designating name to the board, as for instance, 
" a 40-strap-double-spring-jack-board." 




^ i^ l^ i®) ^ 






> 






A series of such spring-jacks arranged on a separate board is shown in Fig. 60. 
In that figure a spring-jack "wedge" is shown in position. The wedge is usually 
formed of two flat, metal strips, insulated by a hard rubber strip from each other. 
The upper strip is shown at b; the under strip is directly beneath b. Two insulated, 
flexible conductors within one cover, c, are joined separately, by suitable means, each 
to one of the metal strii:>s on the wedge. To take off some of the strain from the 



SWITCH BOARDS. 



79 



flexible conductors a piece of stiff rubber tubing r, is placed over portions of the in- 
sulated handle i of the wedge and the conductor. The wedge proper is about 4 inches 
long, I inch wide and | inch thick. 

■ Referring again to Fig. 58, s, s, etc., represent the vertical brass straps. The 
dotted lines represent the horizontal strips behind the board, and which are metallical- 
ly connected with the discs d. Pin plugs are shown inserted at f and x x, 

FIG 59. 




J is a spring- jack, connected by " office " wire, (that is, a pliable, insulated wire) 
at p, to the strap 2. j' is also a spring-jack. The jack is hinged as shown, and is 
capable of being moved, as at w, to permit the insertion of one or more wedges. At 
the end of the "double conductor" cord, remote from the wedge, the terminals are 
generally run into separate double connecting binding posts, as at dc, below the 
switch-board, and are thus connected to wires leading to any desired desk instrument 
in the operating room. 

FIG 60. 




SINGLE SPRING JACK BOARD. 

The double spring- jack arrangement allows of the insertion of additional sets of 
instruments into the circuit when desired. For instance, another wedge could readily 
be inserted at x'^ ; the space between the two jacks j and j^ being, in practice, much 
wider than would appear in the figure. Other instances of the utility of the spring- 
jack and wedge will be be found in connection with the '' Davis'' loop switch. Main 
batteries mb, mb^ are connected to binding posts p p^ attached to horizontal strips, as 
shown. Line wires are connected to binding posts z at the lower end of each spring- 
jack. It will be remembered that each vertical strip is equipped with a single or 
double spring- jack, as the case may be. For simplicity but two straps are shown thus 
equipped in Fig. 58. 



3o AMERICAN TELEGRAPHY. 

By means of this switch-board and its attachments, the chief operator, that is, 
the attendant in charge, is enabled to make, with ease, rapid changes in the disposition 
oi wires, desks and batteries. 

In thefigm-e the " positive," or "copper" battery is connected by a pkigat d t, via 
strip I and disc d, to strap 2, thus supplying electromotive force of positive polarity 
to the line wire at binding post zj via the spring- jack J, through one side of wedge 
w, to the desk relay, back to other side of wedge to spring j^. In a similar way any 
other line Avire may be connected with battery m b', by the insertion of a plug at the 
proper place.* 

Should it be desired to put the " zinc, " or "negative " battery to a line wire it 
is done by inserting a ping so as to connect any desired strap with a disc attached 
to the horizontal strip ^. Thus if it should be required to put " zinc " instead of •' cop- 
per" to the line wire now connected with spring-jack j^, it would only be necessary 
to remove the plug from d f and insert it in the next aperture above," namely, a. 

As each wire entering the office is attached to the binding post of some one 
strap, it is plain that by the removal of a wedge from one spring-jack to another 
any instrument on any desk may be speedily put into the circuit of any desired wire, 
since, as already said, each desk instrument is "connected up" with a Avedge at 
the switch board. 

For large offices these switch-boards are made in sections of 40 to 50 straps 
and 15 to 30 horizontal rows of strips and discs. In some cases also the straps are 
connected by office wire from screw post p to post z and the line wire is then con- 
nected to the post at the back of spring-jack j; but this does not appear to serve any 
useful purpose and is wasteful of " office " wire. 

The battery, or e. m. f. for the oj^eration of duplex and quadruplex circuits is 
brought directly to the operating room table or desk and is not "j)lugged" on at the 
switch. This being the case, " quadruplex "switch cords require but one conductor 
and one strip of metal on the wedge. An instance of that arrangement is shown at 
Q, Fio\ 58, where, it may be seen, the circuit from the duplex or quadruplex set 
passes through the cord and thence to the spring-jack and line wire. By thus insulat- 
ing one side of the wedge it leaves the strap 7 free to be used for other purposes with- 
out interfering in any way with the quadruplex circuit. To permit such use more 
effectually the quadruplex wedge in q might be inserted at q^. 

It is sometimes desirable to be able to insert an "intermediate" battery in a 
circuit which, as in the case of a " through " wire, does not terminate at the switch 
board. The intermediate battery b, attached to the horizontal straps ^ ^^ , as shown, 
is placed in the circuit of the two wires desired, in this instance the wires attached 
to straps 4 and 5, by the insertion of the plugs at x, x. Should it prove that this ar- 
rano-ement of the plugs does not cause the battery b to coincide in polarity with the 
batteries at the other end of the circuit, the battery b may be "reversed " by remov- 
ing the plugs from x x toy y. 

In some large offices as many as 5, 6 or more 50 strap sections are in use, 
placed side by side or in different parts of the room as required. 

When placed side by side it is easy to connect together two remote circuits on 

* Where dynamos are used the ^Yi^es from the machines are brought to certain discs on the switch-board, as indicated 
at e, d. Fig. 58. These discs are not connected together by the horizontal strips behind the board. Tliis is to allow of the 
insertion of the lamps, or otuer resistance, in eacn cucuit, snown in Figs. 24, 2(5. Three or four honzouial rows of such 
discs are thus set apart. Tne top row is usually allotted to tne first potential: tne second and thud lows to the second 
potential, on account of the greater number of circuits fed from that potential. The fourth and fifth potentials, being 
mottly employed on long quadruplex circuits, are not, as a rule, brought to the switch- board, but to tiie desks direct, as in 
the case of gravity battery. Otherwise the arrangements on the switch-board are not practically changea. 



SWITCH BOARDS. 5 1 

the switch board by joining the proper horizontal strips of the different sections, either 
by a suitably arranged plug or by a piece of wire. Thus^ in Fig. 58, assuming the 
straps I to 7 to belong to one section e, and straps 8, 9 to an adjoining section w, the 
two liorizontal strips, c c and b b are shown joined to carry battery to the adjoining 
sections. The lowest liorizontal strip is the "ground" strip, by means of which, and 
a pin plug, any of the Avires may be grounded without battery. This strip is also 
connected throiio-h to both sections e w. 



WAY OFFICE SWrrCH BOARD. 



A form of switch much used in " way " offices, as distinguished from terminal or 
main offices, is shown in Fig. 61. The wires are, as a rule, led into the switch at the 
upper binding posts and into the instruments on the right hand side of the board. 
By means of pin plugs the desk instruments may be placed in the line or not, as 



FIG. 61 



-2^ 




WAY OFFICE SWITCH. 



desired, or the line may be caused to pass through the switch only, by inserting a pin 
in the corresponding aperture, a, between the two vertical bars at the lower end of the 
board. The vertical row of binding posts on the right are connected behind the 
board to the notched discs, as shown by the dotted lines. 



82 



AMERICAN TELEGRAPHY. 



Many different combinations will suggest themselves in connection with this 
switch ; for instance, if, as is often the case, it is desirable to have a way office 
" cut" in on any one of the wires passing through the switch -board it may be quick- 

FIG. 62. 




WAY OFFICE SWITCH. 

ly done, if the line wires are arranged as in Fig. 62. 

By the use of "split" plugs sp, the "testing" instrument, or any of the instru- 



SWITCH BOARDS. 83 

ments connected with one of the phigs, may be readly cut in on any of tlie wires. 
One such plug is shown " cut in" on wire 5, thereby inserting " test " instrument n 
in the circuit. 

A split plug sp, is shown as attached to the relay at right of Fig. 62, and separ- 
ately in Fig. 6^. In the latter figure c c^ are the insulated wires passing into the 
insulated handle /and which are connected to the brass segments b b^, which latter 
are insulated from each other by the insulating material /'. Of course, care must be 
taken to turn the split plug in the aperture of the switch so that it will not " short 
circuit" the relay out of the main line circuit, as would result if one half of the plug 
touches both the strip and disc. 

FIG. 63. 




ROUND SPLIT PLUG. 

Lightning arresters l a, Figs. 61 and 62, consisting of flat, metal discs, which 
are connected by a strip behind the board with the ground, are placed in close 
proximity to the upright straps. [See "Lightning Arresters"] 

WAY OFFICE CUT OUT. 

A common form of cut-out switch for one-wire way offices is shown in Fig. 64. 

FIG. 64. 




WAY OFFICE CUT-OUT. 



It consists of a metal strap s, placed on a small base board. On one end of 
the strap a short pin p is attached. A similar pin /^ is set in the base board. 
At rest, the tension given to the strap brings/ snugly against /^ The s])lit j.hig 



84 



AMERICAN TELEGRAPHY. 



p, shown separately in Fig. 65, is grooved on its sides to fit the pins / /^, and 
it is capable of being pushed down between the latter. The office instrument is con- 
nected by suitable wires with the respective sides of the split plug; one half of the 
piug being insulated from the other half. 



FIG. 65. 




SQUARE SPLIT PLUG. 

The line wire is brought to two binding posts lw lw^, on the base board, lw'- 
is connected under the base to the strap s. lw to the pin /^. Thus when the plug 
is inserted between the 23ins,the office instrument, or relay, is put in the line wire 
circuit. When the plug is withdrawn the relay is cut out and the line wire is closed 
automaticaiiy by the contact of the pins. 



LIGHTNING ARRESTERS. 

Many of the so-called lightning arresters in use on telegi-aph circuits might, 
perhaps, more correctly be termed lightning " deviators," since the object of their 
use is not so much to arrest the lightning as to cause it to deviate from the path lead- 
ing to earth through the instruments to another path leading to the earth directly. 

Such lightning "arresters " are those which are placed near to, but not indirect 
contact with the telegraph wire to be protected. They frequently consist of a strip 
of brass, Fig. 66, connected by a wire directly to the earth e. Right above, or be- 
side this strip, but not touching it, is placed another strip of brass forming a part of 
the line circuit. The strips are separated by a small airspace having high resistance. 
The intention is that when the line is highly charged by lightning the electricity will 



LIGHTNING ARRESTERS. 



85 



jump over this short air space of high resistance in preference to following the, elec- 
trically, shorter route to earth through the instruments. And, taking advantage of 
the tendency of electricity to jump from sharp points, the side of the strip connected 
with the line is made with a serrated edge to facilitate the desired action. 



FIG. 66. 




In other forms of lightning ''arresters," the line strips, as indicated in Fig. 67, 
are placed upon a " ground " strip with only thin layers of parrafin paper interven- 
ing. In this form the lightning discharge, in passing to the earth, ruptures the par- 
rafin paper. The manner in which the plates are separated by this paper is shown 
more clearly by the black line between plates p and E,in Fig. 70. 





FIG. 


67. 


To Ltrte 




. ^Tfe 




s^ 




To In^^nurienZs 



In many way-office and other switches, a disc form of " arrester '■ is used, one 
disc, connected to the earth, being placed over two strips. The discs r> d, Fig. d^, are 
screwed on to the ground strip p (which runs horizontally the length of the 
switch-board, on the back of it) but do not touch the line strips s, s etc. on the front 
of the board. Fig. 68 represents a front view of the apparatus; a side view, or cross 
section of the same may be seen in Fig. 69. 



86 



AMERICAN TELEGRAPHY. 



In the latter figure the separation of the discs d from the strips s s is plainly 
shown. 

Combination plate and ''spider" aekestee.— Another form of lightning 
arrester consists of a fine wire of some alloy, such as German silver, inserted in the 
line wire at the switch. This is generally placed as an auxiliary to the forms of 
*' arresters " previously described. This wire has a higli resistance as compared with 
the rest of the circuit and is either disrupted or fused by the passage of an unusually 
strong current of electricity. When this happens the " lightning " may fairly be said 
to be "arrested." 

FIG. 68. 




ARRESTER ON SWITCH-BOARD. 



This combination arrangement of fuse and ground plate, shown in Fig. 70, or 
Modifications of it, is now almost invariably used in " cable boxes " and " cable 
houses," and on the cupolas of telegraph offices, and it is being extensively introduced 
on switch-boards. The wire used has a diameter of about "5 to 7 mils, equal 



FIG. 69. 




to No. 32 or No. s^ B. w. G. A mil is the one thousandth of an inch. The binding 
screws b s, to which the fine wire is attached, are specially constructed to hold the 
wire without injury. These screws have double connections, one for the line wire 



LIGHTNING ARRESTERS, 



87 



proper at x, on the main body of the binding post, and the other, on the top, con- 
sisting of a set screw arrangement for the fine wire. Some care is necessary in con- 
necting up the German silver wire. The connection may be facilitated by giving 
the wire a few spiral turns around a small roll of card paper, which will give the 
wire a slight tension, and, at the same time, provide a small surplus upon which to 
draw in tightening the set screws. The tension is useful in that it may assist in 
the disruption or separation of the wire under a strong current. This wire is known 
as the "spider " wire. It would now be used, even if not" effective as a lightning 
arrester, as a fuse Avire, to protect the office apparatus in the event of a cross with 
an electric liglit circuit. 

The arrangement in Fig. 70 dispenses with the employment of one row of 
binding screws, three rows having been employed formerly. It will be under- 



FIG 70. 



SMslramf^ 




stood that the wood-screw of b s^ is not connected with anything but the wooden 
base. The ground plate e and the brass plate p correspond to tliose shown in top 
view, Fig. 67, the brass plates p being separated from the ground plate e by parrafin 
paper. 

Mag^^etic lightning arrester.— Still another form of lightning arrester 
in use in the telegraph service of this country, and one which is used also as a pro- 
tection against electric light or other strong currents, is shown in Fig. 71. It is a 

FIG 71. 



Jo/^cs^ume^y 




To Zi/f^ 



"magnetic'^ lightning or current arrester. The line wire is connected at screw 
post s^, with the ap[)aratus, wliich is mounted on a narrow base board n. Tlie screw 



88 AMERICAN TELEGRAPHY. 

rests on a brass strip attached to the base board. A strip of brass s, hinged at P, 
extends to the catch c which is rigidly attached, as shown, to the armature of 
the electro-magnet M. Tii ere are but a few turns of wire on the electro-magnet. 
The strip s is given a constant tendency to spring away from c by the spiral sprin_^ 
at X, The spring x normally holds the catch on strip s. Ordinarily, the line cir- 
cuit includes the strips p, s, the catch c, the armature and the coil of the electro- 
magnet. The adjustment of the retractile spring x is such that the armature is not 
attracted until an unusually strong current passes in the electro-magnet, when the lat- 
ter attracts its armature. This act releases the strip s which springs away, opening 
the circuit at c, thereby, if the action has been prompt enough, j^i'eventing injury to 
the office instruments. 

Objection is sometimes urged against this class of arrester on the ground that 
it is prone to open the circuit on slight cause, and does not always do so when it 
would be beneficial, which state of affairs is doubtless due to improper adjustment 
of the apparatus. It is also claimed that it is inoperative in the presence of acciden- 
tal contact of an alternating current circuit since the rapidity of the alternations 
prevents the magnet from acting upon its armature. 

Electko -THERMIC AKEESTER. — An aiTcstcr sliowii in Fig. 72 has recently been 
devised to respond to either continuous or alternating currents. It operates in con- 
formity with the laws that, when a powerful current, continuous or alternating, flows ia 
a wire of high resistance its temperature rises and the wire expands. 

FIG. 72. * 



^ 




7d/as(rumenfy 




In the figure, w is a short wire of high resistance always in the circuit. S is a 
bent lever hinged at x^ and normally held against the up-stop c, a short distance from 
p, by the tension of the wire w. When, however, the wire w is heated by a strong 
current it expands and permits the lever s to drop on the contact p, which is connect- 
ed with the earth, thereby diverting the current from the apparatus to be protected. 

The ARGUS lightxij?-g arrester. — This arrester, which is now largely used by 
the Western Union Telegraph Co., is shown in Fig. 73^. It embodies some 
features which have been found of advantage. It has but few metal parts, and these 
are mounted on a porcelain base, B. It employs a small coil of bare copper wire w w 
wound in a spiral groove on a porcelain cylinder. A ground plate G is placed over 
the coil as indicated. This coil, as well as a fuse ware F w, is interposed betw^een 



LIGHTMXG ARRESTERS. 



89 



the aerial line l and a cable or the office instruments A. The ground plate is ad- 
justed over the coil so that the end nearest the line is about an eighth of an inch 
from the b^^re wire, while its other end is about the thirty-second of an inch from the 
wire. This is done for the purpose of distributing the lightning discharges over the 
whole of the coil, whereby no damage results to any one part of the plate or coil. 




By this arrangement the line is freed of the lightning charge without interruption 
to the service, and without the necessity of frequent attention to the arrester. The 
fuse wire is mainly emj^loyed to prevent damage to the apparatus or cables, in case of 
contact with an electric light or power wire. The current-carrying capacity of the 
luse wire is about 4 or 5 amperes; above that it fuses. 

Carbo:n-block fuse lightning arrester. — In Fig. 73<2 is shown a form of 
arrester that has been used a good deal in telegraph and telephone practice. In 
the figure, f is a small fuse wire carried on a thin strip of mica m, tipped with metal 
at each end, and held by metal clips as shown, c represents two small carbon blocks 
separated by a thin sheet of mica. These blocks are held in position by the metal 
springs shown. The left-hand block is connected to ground at g; the right-hand 
block is connected to the wire or apparatus at A. A wire from A leads to apparatus. 




The line wire is connected to L. Thus a heavy current coming from the line Avire 
will fuse F, and a lightning discharge will jump to ground by way of the carbon 
blocks. When the fuse is blown the ndca strip is removed from the springs and a 
new strip is inserted. The effect of a lightning discharge through the carbon blocks 
is to create some carbon dust, to remove which the carbons are taken out of their 
springs and the dust brushed off, when the carbons are again ready for service. The 
carrying capacity of the fuse wire may also be about 4 or 5 amperes. 



CHAPTER VI. 



THE CONDENSER — STATIC CHARGE — DISTRIBUTION OF, ETC. ^INDUCTION, MUTUAL, SELF^ 

ETC. — THE RHEOSTAT. 



THE CONDENSER. 



Theor}^. — When by any means an insulated conductor is charged with electricity, 
whether by friction or by the application of a battery or other source of electricity, 
it is found that it will excite or, as it is said, " induce," in any neighboring conduc- 
tor a charge of electricity. It is further found that if the electricity in the first body 
be " positive," that induced in the neighboring body will be ''negative." For ex- 
ample. In Fig. 74,if the insulated metal plate a be charged by the positive pole of 
battery b it will induce in the adjoining plate b a charge of negative polarity. 

Such an arrangement of plates is termed a " condenser," and one of the most 
useful and indispensable instruments employed in multiplex, printing, and automatic 
telegraphy, and in electrical testing, is based on the foregoing fact. 

If the battery <?, Fig. 74, be removed and the wire connectiug it with a be in- 



r 



sulated, the plates will retain the charge for a certain time, depending on the degree 
of insulation of the plates. If that were perfect the charge would be held indefinite- 
ly. In practice this degree of insulation is not procurable, so that, even as regards the 
best of condensers, the charge is gradually dissipated. If, on the other hand, 
the battery be removed from plate a, and the two plates be at once joined by a wire, 
a momentary current will pass in that wire;and it will then be found that both plates, 
by that act, have been discharged of their electricity. 

The electricity induced and held in the plates of the condenser in the manner 
stated is termed " static " electricity. 



THE CONDENSER. 



91 



The quantity of electricity thus accumulated in, or at the plates, is proportional to 
the electromotive force of the charging battery and to the "capacity" of the con- 
denser. 

The '' capacity " of a condenser is i^.s ability to contain, or accumulate a certain 
amount of electricity under a given electric pressure. The capacity may be likened, 
for example, to that of a gas meter which, under a certain pressure, will contain a 
certain number of cubic feet of gas. At such a time we may speak of the meter 
as being filled with gas while yet it may be capable of containing much more gas 
under a liigher pressure; gas being a compressible fluid. Thus, we may say, in 
the case of such a meter, the space enclosed by which is, say, i cubic foot, that 
under a pressure of i lb. it will hold a cubic foot of gas. Obviously, a meter en- 
closing 2 cubic feet of space will contain double the amount of gas, at the same 
pressure. 

Gas is measured, as to quantity, in terms of cubic feet. Water in terms of 
the gallon, etc. Analogously, electricity is measured, as to quantity, in terms of the 
coulomb', a coulomb being that quantity which will flow past a given point in a cir- 
cuit in I second, when the current strength is i ampere. When an electrical condenser, 
under a pressure of i volt, holds, or accumulates, i coulomb of electricity, it is said 
to have a " capacity " of i farad; farad being the unit of electric capacity. 

The capacity of a condenser varies with the distance between its opposite plates ; 

FIG. 75. 




being greater the nearer they are together. It increases, other things being equal, as 
the size of the plates is increased. The capacity is also found to vary with the insulat- 
ing material, or dielectric, employed between the plates; being greater, for instance, 
if the space be occupied by glass, india-rubber or gutta-percha, than if occupied by 
dry air. 

This property of insulators, or dielectrics, which permits this so-called inductive 
influence to take place through them, or by which the inductive influence is effected, is 
termed " inductive capacity." The property which this inductive capacity of a 
dielectric imparts to conductors is termed "electro-static capacity." 

The inductive capacity of air is taken as the standard by which that capacity in 
other dielectrics is compared. 

Air being i, the " specific inductive capacity " of paraflin is found to be about 



92 



AMERICAN TELEGRAPHY. 



2; india-rubber 2.5 ; glass 3.25. etc. 

The electrical coudeiiser, as employed in telegraphy, is generally constructed of 
thin sheets of tin-foil which are separated from each other by an insulating material 
such as parrafin paper or mica. 

In order to secure a large area of conducting surface, thereby to increase the 
capacity, the alternate tin-foil plates are connected as outlined in Fig. 75, the plates 
of the respective series being connected. In that figure the horizontal lines represent 
the alternate sheets of tin-foil ; the blank spaces, the insulating material. 

The practical unit of electro static capacity is the microfarad (the one-millionth 
part of a farad.) The electro-static capacity of 3 miles of Atlantic cable is about i 
microfarad. The electro-static capacity of an ordinary overhead wire is about 
three one hundredths of a microfarad, per mile. 

FIG. 76. 




THEORY OF ADJUSTABLE COXDEXSER, 



In practice it is frequently necessary to be able to vary the capacity of a con- 
denser. To permit this, "adjustable" condensers are so constructed that, by the 
insertion or removal of metallic plugs, more or less plates of tin-foil are brought into 
or cut out of service. 

Fig. 76 indicates the manner in which this variation of the capacity of a con- 
denser may be accomplished. A desired number of the sheets of one series of plates 
is connected in groups and each group is then connected, separately, to brass pieces 
p^ as at 8, 16, 32, 40, 80, in the figure. A strip of brass s, provided with niches for 
metallic " pin " plugs, faces the pieces p. By the insertion of pin-plugs any one or all 



THE CONDENSER. 93 

of the groups can be connected with the brass strip s. In the figure, groups 8 and 
32 are thus connected, the other groups being left inoperative. All the "ground" 
plates are joined together and brought to the screw-post g, but only so many of them 
as may be opposite the groups joined to the strip s will be "active." The external 
connections of the condenser are made at the screw posts h and g. 

Standard a:kd commercial condensers.— The form of "standard" condenser 
usually employed in testing is represented in Fig. 77. The capacity of such con- 
densers IS generally | or ^ microfarad. 

FIG 77. 




STANDARD CONDENSER. 



The ordinary condenser used in telegraphy is illustrated in Fisf. 78. The capacity of 
these condensers is generally stamped on their ends — it ranges from |^ to 10 or more 
microfarads. 

FIG. 78, 




ADJUSTABLE COXDENSElt. 



Fig 79 is a form frequently employed in the Wheatstone automatic duplex sys- 
tem. A modification of this form also is shown, theoretically, in chapter on the Wheat- 
stone automatic telegraph system. 

Ordinary condensers such as are used in duplex and quadruplex telegraphy are 
required to have an insulation resistance of about 40 megolims, per microfarad, after 
one minute of "charging," or electrification. (See Chapter XXXI, ajid 

also remarks at end of this section.) For example, a condenser of 5 microfarads 
capacity, having a total insulation resistance of 8 megohms, will meet the require- 



94 AMERICAN TELEGRAPHY. 

ments of 40 megolims, per microfarad. Condensers may be tested for capacity by 
the method described in connection with Capacity tests. 

When a number of condensers are joined, in the manner, for instance, in which 
the plates 8 and 32 are connected in Fig. 76, they are said to be connected in mul- 
tiple, and, thus connected, each set of plates adds to the total capacity proportion- 
ally to its capacity. In other words, each condenser adds to the total capacity 
virtually as each conductor connected with others in multiple adds to the total conduct- 
ance of the circuit; hence the joint capacity of condensers in multiple is equal to the 
sum of the respective capacities of the condensers. 

FIG. 79. 



WHFATSTONE CONDENSER. 



^ When condensers, as for example, c^, C2, C3, are connected as in Fig. 80, in 
which the iinier tei-minal of one condenser is joined to the outer terminal of the 
other, throughout, they are said to be connected in series, or " cascade. " 

lu telegraphy it is rarely necessary to connect condensers ia series. In testing 
it is sometimes done to secure a greater variation of "capacities." The rule for 
finding the total capacity of condensers, in series, is similar to that for finding the 
joint resistance of conductors in multiple, namely.— 

The totals 07 resulting capacity of cojidensers in series is equal to the reciprocal of the 
sum of the reciprocals of the respective capacities of the cofidensers, {See Joint Resistance.) 

Condensers may be tested for insulation resistance by the direct deflection meth- 
od of measuring high resistances. 

The insulation resistance of standard condensers may be made very high, in some 
cases a resistance amounting to 8000 megohms, per microfarad, has been attained. 

Electktfication. — When a battery is applied to the terminals of a condenser, 
in which the dielectric is, for instance, paraflin, india-rubber or gutta-percha, it is 
noticed that the current does not immediately die out, but decreases gradually. In 



THE CONDENSER. 



95 



some condensers indications of a decreasing current are still observable at the end of 
several hours, and on discharging such condensers the first strong current of discharge 
is followed by a gradually decreasing current in the opposite direction to that of the 
current of charge. 

This phenomenon is termed electrification. It is referred to elsewhere as being 
very noticeable on gutta-percha, and india-rubber covered cables. It is not, however, 
noticeable, or but very slightly, in condensers in which the dielectric is air, and but 
to a slight extent in the best make of standard condensers; the currents of charge 
and discharge in such cases being of momentary duration. 

FIG. 80. 




CONDENSERS ARRANGED IN SERIES, OR CASCADE. 

This phenomenon, electrification, is supposed to be due to the gradual " polarb? 
ation " of the dielectric, in other words, to the setting up of a counter-electromotive 
force in the dielectric opposed to that of the charging battery, the result being that 
the current through the dielectric is gradually reduced, in a manner, at least, analo- 
gous to that in which the current is reduced by the polarization of a voltaic celL 
When electrification has ceased, or after it has progressed for a stated time, {See 
Chan. XXXI ) the resistance of the condenser is calculated. 



STATIC CHARGE, DISTEIBUTION OF, ETC. 

When electric pressure is applied to the terminal of a conductor such as a tele- 
graph wire, or cable, tlie latter receives a " charge " of electricity after the manner o^ 
a condenser. Such a wire or cable may, in fact, be considered a condenser, the con- 
ductor being one of the plates and the earth, water, or the armor of the cable, the 
other plate; the air or other insulating medium between the conductor and eartli or 
the armoi serving in the same capacity as the insulating medium, or dielectric, of the 
condc!iser. 

Thus, such a conductor possesses, in addition to " resistance, '' the property of 
electro static capacity, by virtue of which it takes a static " charge." 

The static capacity of a wire or cable varies with its length and, as in the eaj^*^ 



96 AMERICAN TELEGRAPHY. 

of a condenser, witli the area of the surface of the conductor, and with the nature 
and thickness of its insulating covering. The static "charge" of a wire or cable, 
varies directly with its static capacity and with the .electromotive force. 

When electromotive force is applied to the terminal of a long conductor, or 
cable, the other end of which is " open," there will be at first a sudden inrush of 
electricity due to the " charging '' of the conductor, but afterwards the current di- 
minishes more or less graduall}^, according to the extent that " electrification " takes 
place. When the electromotive force is applied to the terminal of a conductor, the 
other end of which is placed to earth, the first rush of current is partly due to its 
electro-static capacity; the normal current which follows is explainable by Ohm's law. 

When a " steady " current is flowing in a circuit it is known that the potential, 
or pressure,falls in direct proportion as it " overcomes " resistance. For example, if, 
in Fig. 8 1, the line r represents the resistance of a wire of, say, lOO ohms, from x to y, 
and the perpendicular line a, the electromotive force, loo volts, of the circuit, and if 
the wire be grounded at y, the fall, or " slope " of potential, as it is also termed, will 
be represented by the line f. If then the pressure, at x, is lOO volts, at a point along 
the wire, say, 50 ohms from x, that is, midway of the circuit, it will have fallen to 
50 volts, and at any other selected point of the circuit it will be found that the 
pressure will have fallen in direct proportion to the resistance overcome. 

The extent to which the potential has fallen at any point of a circuit may be 
graphically shown by a diagram such as Fig. 81, and as recourse to similar drawings 
will be frequently had in the course of this work to facilitate certain explanations, 
it may be well to dwell further on the subject here, {see also Wheatstone bridge.) 

For example, assuming the vertical line a to be subdivided into 100 parts, each 
representing i volt, and the line Einto 100 parts, each representing i ohm, if a ver- 
tical line be drawn from any point on e, say, at o (50 ohms) to the line f, and a 
horizontal line be then drawn from the intersection of that vertical line with the line 
F to the line a, the horizontal line will touch a at a sub-division corresponding to the 
potential on the wire at o, namely, 50 volts. (The wire being to earth at y.) 

In practice the term electromotive force is now often used to indicate the total 
electromotive force in a circuit. The term " potential difference " is used in refer- 
ence to the difference of potential, or pressure, that exists between any parts of a cir- 
cuit. For instance, in the example just given, the "electromotive force" of the 
circuit is 100 volts; the "potential difference, " or difference of potentials, between x 
and o is 50 volts; that between o and y 50 volts also. 

A wire or cable also, like a condenser, takes a charge proportional to the differ- 
ence of pressure at its respective plates; the plates, in this sense, being the conductor 
proper and the armor or earth. Consequently, as the potential, or pressure, falls in a 
conductor in direct proportion as resistance is overcome, it follows that the static 
charge of a wire or cable is not, under all conditions, the same at each point of its 
length; as will, perhaps be clear by further reference to Fig. 81. 

For example, assuming first that the positive pole at x is placed to the line and 
that the latter is grounded at y, the slope of potential, as before, is represented by 
the line f. Hence, lines drawn from the point a on k to the line F and tlieuce to 
A, will indicate the potential at that particular point to be about 66.6 volts. Other 



DISTRIBUTION OF CHARGE. 



97 



lines drawn similarly from e at the point b will show the potential at b to be 33.3 
volts, etc. 

If then we should attach, as indicated in the figure, condensers c, and galvanom- 
eters G, of exactly similar capacities, respectively, to the wire r at points x, ^, b and 
Y and should measure the potential difference at those points in the usual way * we 
would find that at X it would be 100 volts; at i, 66.6 volts; at 2, t^t^.-^^ volts, while 
no difference of potential would be perceptible at y. 

Calling, for the purpose of illustration, the capacity of each condenser t, the 
charge accumulated in the condenser at x would then be 100; that at a would be 
66.6; that at ^ would be 33.3, while the charge of a condenser connected with the 
wire at y would be nothing, since in that case the wire is at zero potential. The 
total charge of the condensers will be equal to the sum of their respective charges. 

Since, then, a conductor in taking a charge acts like a condenser, it follows that, 
under the conditions of battery and wire stated, and assuming each portion of the 
conductor to have an equal electro- static capacity, the charge at point x of the conductor 
would be the maximum; at unit portion a it would be \ less; at unit portion b it 
would be f less, while at unit portion y the charge would be zero. Similarly, for 
any other particular portion of the conductor the charge will be found to vary with 
the potential of the conductor at that portion, and the total charge of the conductor 
will be equal to the sum of the various charges at each portion of the conductor. 

As pointed out by Sir Wm. Siemens, the sum of those charges may be repre- 
sented by the superficial area of the triangle a f k, Fig. 81. 



FIG. 81. 



100+ 




DISTRIBUTION OF "CHARGE. 



The superficial area, or surface enclosed by a triangle is equal to one-half the pro- 
duct of the altitude of the triangle by its length; in other words, it is equal to one-half 
the superficial area of a square or parallelogram having similar altitude and 
length. Hence, if, for example, we assume the capacity of a conductor, say, 500 
miles in length to be, in round numbers, i microfarad, per mile, its total charge, 
or quantity of electricity accumulated, with an electromotive force of 20 volts, would 

be ^- = 5000, that is assuming the conductor to be " grounded " at one termi- 

2 

nal. The potential of the same conductor with its distant terminal open, or with the 

* (See Electrical Testing,) The condensers and ualvauonu'tfrs need not be of similar capacity unless the readings of the 
various galvanometers are to be compared to that at X, wliere the i)otential is known to be 100 volts. The potential at 
these points might also be determined by noting the detleetion of a galvanometer due to a condenser charged by 1 volt from 
a gravity cell, for instance, and comi)arhii;; that iletlection with the deflection caused by the same condenser when attached 
to the line wire. If, for exa.mi)le, the dertection diie to 1 volt should be 10 divisions and that due to the line 500 divisions, 
the potential of the line at that i)oint would be 50 volts. 



98 AMERICAN TELEGRAPHY. 

positive pole to line, would be equal at all points, and may be represented by tbe line, 
z, in Fig. 8r. The total charge of the conductor in this case maybe repre- 
sented by the parallelogram a z p r; in other words, the charge with the wire 
open is double that with one terminal to ground. In both of these cases, since the 
charging electromotive force is assumed to be positive, the charge would also be 
positive. 

If a negative pole should be placed to the line at y, Fig. 81, the fall of pressure 
along the conductor would be indicated by the line n n' and the charge from x to 
o, which would be positive, would be proportional to the area of the triangle a k n; 
while the charge from o to y, which would be negative, would be proportional to the 
area of the triangle b r n', and the total charge of the conductor would be equal t j 
the algebraic sum of those charges, and these " charges," if allowed to unite, or mix. 
would nullify each other. 

It may be noted here that although the "potential" at various points of the 
conductor, may, under certain conditions, be of different values, the current strength 
in a conductor is equal at all points, as may be proven by the insertion of similai 
galvanometers, G g', at the opposite ends of the circuit e, when it will be found that, 
while a steady current is flowing in the wire, those galvanometers will each show 
an equal deflection. 

Static charge of a conductor. — The statement that the static " charge " of a 
wire or cable varies directly with the electromotive force may be illustrated by the 
aid of a diagram. 

FIG. 81 a. 




waY 



In Fig. 8 1 iz, let k represent the resistance of a conductor of two sections of equal 
length, having a resistance of 50 ohms each; v the electromotive force at x. 

First, taking the conductor from x to x, grounded at x, with an assumed electro- 
motive force of 10 volts, the total charge, that is, the sum of the various charges at 
all the points, may be represented, as in the previous section, by the triangle a d c, 

1 10 X so 
namely, ^ — = 250. 

2 
Second, doubling the length of R, but retaining the electromotive force at 10 

rolts, the charge will now be represented by the triangle a b r, namely, — — — i^ 



MUTUAL INDUCTION. 99 

= 500. 

Third, doubling the electromotive force, r remaining 50, the charge will be 

represented by the triangle v b b; namely ^- —= 500, micro-coulombs. 

2 

The total charge of a wire or cable with distant terminal " open " may be ex- 
pressed by a formula, thus : 

Q = E X K X L, where q is the total charge in coulombs, e the elect/omoti^e 
force in volts, K the capacity of cable, per mile, in microfarads, and l its length, in 
miles. 

With the distant terminal to ground the total charge may be represented thus: 

_ E X K X L 
2 

The manner of ascertaining the static capacity of a conductor is described under 
chapter on Electrical Testing. {See Capacity Tests.) 



MUTUAL INDUCTION BETWEEN PARALLEL WIRES — SELF INDUCTION. 

Electro-magnetic mutual induction. — When an electric current flows in a 
wire it is observed tliat variations in the strength of current have the effect of 
"inducing" momentary currents in adjacent parallel wires. 

For example, in Fig, 82 let a and b be two parallel circuits; l> the battery or 
other source of electromotive force, in a. 

If the key k be opened and closed at intervals it will be seen by the deflections 
of the galvanometer g that " current " is, at such times, setup in b, and that the cur- 
rent set up when the key is closed is opposite to that originated when the key is 
opened; and further, that the current originated in b, at the "closing," is opposite in 
direction to that of the current due to battery /^. 

This eflect, or so much of it as may be electro- magnetic, and which is termed 
''mutual induction,"* is explained by the fact that the magnetic lines of force wliich 
emanate from a wire conveying a current, in rising and falling, " cut " the parallel 
wire and induce in it currents which vary in strength with the current flowing in the 
first wire. 

The induction coil used so extensively, among other ways in connection with the 
telephone transmitter, is an instrument constructed to avail of the mutual electro-mag- 
netic induction between parallel wires. The turns of the first wire, or the '' primary, " 
in which the battery is placed, being adjacent to the "secondary" wire, the makes and 
breaks, or rapid variations in the strength of current of the primary circuit, *' induce" 
currents of opposite polarity in the secondary coil. A core of soft iron is embraced by 
the coils to increase the density of the magnetism and thereby to increase the strength 
of the induced current as the lines of force increase and decrease, in rising and f alii n^r 



Eleciro-magneiic 



100 



AMERICAN TELEGRAPHY. 



Electkostatic mutual ixductio>''. — It has already been stated that when a 
conductor of electricity receives a "static"' charge, it induces in a neighboring con- 
ductor, as^ for instance, B in Fig. 82, a charge of opposite polarity to the charging 

battery or e. m. e. The charge in b is 
Fig. 82. due to static induction. In the act 

of taking this charge a momentary 
current is established in B, and when 
the orio^inatino^ charade is withdrawn a 
momentary current in the opposite 
direction is set up in B. a and b are 
virtually plates of a condenser corre- 




^ A_ 



sponding to A, B, Fig. 74. These 
currents are due to electrostatic mutual induction. 

Inductaj^ce, capacity, reactaxce, imped axce. — It is known that in a tele- 
graph line or other conductor in which there are electromagnets, the current is 
retarded in rising when the circuit is closed, and that its fall is prolonged when the 
circuit is opened, thus producing a retardation of the signals. This is due to the 
inductance of the circuit, or self-induction. The explanation is that the magnetic 
lines of force which in rising and falling set up currents in a parallel conductor, 
also cut the wire in which the current that produced the lines of force is or was 
flowing. The sudden collapse of the magnetic lines of force at the opening of the 
circuit induces in the wire a momentary electromotive force which sets up an "extra " 
current or a prolongation of the original current ; that is, the current of self-induc- 
tion at the opening of a circuit is in the same direction as the original current. 
Reversely, when the circuit is closed and the lines of force are rising they tend to set 
up an E. M. F. opposed to that of the battery or dynamo, with the result that the 
current does not attain its full strength immediately. 

The inductance of a given circuit (assuming a circuit without iron, see page 66)^ 
like resistance and capacity of a given circuit, is constant. As stated elsewhere (Hertz 
oscillator), inductance is analogous to mechanical inertia, while capacity is analogous 
to mechanical elasticity. With a continuous current, inductance and capacity have 
no effect upon the current, but when the current is varied, or alternated, their effects 
come into operation. In a circuit in which there is only resistance, the current 
rises and falls with the e. m. f., and is therefore said to be in phase with it. AYhen 
there is resistance and inductance in a circuit the effect of inductance is, as stated, 
to retard the rise and fall of the current, so that it is said to lag behind the dynamo 
or battery E. M. F., by an angle depending on the inductance E. M. F., as indicated in 
Fig. 82«, in which the solid curve represents the E. M. F. wave, and the dotted curve 



Fig. %2a. 



Fig. 82^. 





the current wave, and as explained in connection with Fig. ^20. (A complete period 
or cycle of a current wave from zero, to positive maximum, back to zero, to negative 
maxmnmi and back to zero constitutes two half cycles of 180° each, to o\ Fig. 82^^.) 
When there are only resistance and capacity in a circuit the effect of capacity is like 
that property of a spring which resists bending but assists in the restoring move- 
ment; hence it hastens the rise and fall of a varying current so that it precedes or leads 



INDUCTANCE, CAPACITY, REACTANCE, IMPEDANCE. lOoc^ 

the dynamo E. m. f. by an angle depending on the capacity e. m. f., in which case 
the solid line in Fig. 82« would represent the current wave and the dotted line the 
dynamo e. m. f. wave. Therefore if the inductance and capacity effects of a circuit 
are equal the current will rise and fall with the dynamo e. m. f. (examples of which 
will be mentioned later), inasmuch as their joint effect upon the current is nil. 

Capacity and inductance effects are termed capacity and inductance reactances 
respectiyely. Capacity reactance is also termed condensance. The inductance of 
a conductor depends largely on its form. Thus a coil of wire will have greater 
inductance than a straight wire of the same length, for the reason that the lines of 
force in each turn of the coil act upon all the other turns; whereas the lines of force 
circling around a straight wire cut the wire but once.. Also, tbe capacity of a wire 
conductor depends upon its circumference, its dielectric, etc. {See page 98.) 

In a circuit in which the current is alternating or varying and in which There is 
inductance or capacity, the effect is equivalent to having an opposing e. m. f. in the 
circuit. Hence to obtain a current equal to that which would flow if the current 
were continuous, the dynamo or battery E. M. F. must be increased to compensate 
for the opposing e. m. f. ; otherwise the current will be less than with a continuous 
current. In such cases the dynamo or battery E. M. F. is termed the impressed 
E. M. F. In such a circuit there are to be considered an impressed e. m. f., an 
E. M. F. due to the inductance or capacity of circuit, and an energy or active e. m. f. 
In the case of a primary battery, if two cells of one volt E. M. F. each are placed in 
opposition to four similar cells {see page 26) in a circuit of, say, four ohms resistance, 
the resulting effective or energy e. m. f. is two volts, and the current strength, 
according to Ohm's law, is ^ ampere. The energy E. m. f. referred to is that e. w. f. 
which, multiplied by the current, gives the electrical power, or watts, of the circuit. 
In connection with alternating current practice this E. M. F. is variously termed the 
free, effective, virtual, and power E. M. F., as distinguished from the impressed and 
reactance electromotive forces. In the example given the four cells in series consti- 
tute or are the equivaleut of the impressed E. m. f. of the circuit. 

In an alternating current circuit having indnctance or capacity, the lag or lead 
referred to brings about a condition in which the inductance or capacity E. M. F. is 
said to be in quadrature with or acts at right angles to the energy E. m. f., and the 
impressed e. m. f. corresponds to the resultant, or what is termed the vector sum, 
of those forces {see parallelogram of forces, page 104), and not the numerical dif- 
ference as in the case of the opposing electromotive forces. Fig. 15. (These effects 
of inductance and capacity which, so to speak, place them in quadrature with 
the energy e. m. f. are virtually due to the changes in the magnetic or electrostatic 
fields, or both, around the conductor, and may be considered as operating in a sense 
analogously to the magnetic lines of force in the coil and the earth's magnetic lines, 
respectively. Fig. 85.) 

F'or example, let the line e'. Fig. 82c, represent the inductance e. m. f. of a cir- 
cuit; the line e the energy e. m. f. Then e represents the impressed e. m. f. ; e' and 
e being the components of the resultant e. In other words, e is the hvpothenuse of 
the triangle with sides e', e. The angle x formed by e and e is termed the angle of 
lag, which angle will vary if e or e' vary, as will be shown presently. By geometry 
the square of e is equal to the sum of the squares of e', e, that is, e' = e'^ + E", or 
^ = |/e'^ + e^ (that is, e equals the square root of the sum of the squares of e', e). 
Hence the value of the components of e may be readily ascertained if the values of 
e and either of its components are known, and vice versa, numerical examples of 
which will be given. It is obviously not strictly correct to say that the impressed 
E. M. F. is the resultant of the energy and inductance e. m. f.'s, since these latter 
forces are brought into existence by the former, but it is convenient for the purpose 
to so consider it. By Fig. 826' it may be seen on consideration, and as indicated by 



oob 



AMERICAN TELEGRAPHY 



the dotted lines, that the greater the mdiictance e. m. f. e', with a given impressed 
E. M. F. e, the less Avill be the energy e. m. f. e, and the greater will be the angle of 
lag X between £ and e. For it is clear that e' cannot be increased without detracting 
from E if e remains unchanged. Also the less the indactance e. m. f. e', the im- 
pressed E. M. F. remaining the same, the greater will be the energy e. x. f. e, and 
the less will be the angle of lag x between e ^md e. Hence when e' is entirely 
eliminated the impressed e. m. f. becomes the energy e. m. f. of Ohm's law, which 
law, however, it may be noted, is as operative in alternating as in direct current cir- 
cuits when due allowance is made for inductance and capacity reactances, as will 
be shown in connection with subsequent remarks on impedance. 



Fig. 82r. /' 



Fig. ^2d. 





As stated elsewhere (page 207^), the unit of inductance is the henry, which is 
defined as the amount of inductance existing in a circuit that will develop one volt 
when the current varies uniformly at the rate of one ampere per second. From this 
it follows that the inductance e. m. f. or reactance in a circuit of given inductance will 
vary with the strength of current and with its frequency of variation. For example, 
given an inductance of one henry and a current of one ampere varying ten times per 
second, ten volts inductance E. M. f. will be developed, or if the current be ten 
amperes and varies once per second, ten volts inductance e. m. f. will be developed. 

Hence, e' = x x c x l, and l = , 

X X c 

where l is inductance in henrys, e' is tlie inductance e. m. f., x is the rate of varia- 
tio.n (or, more correctly, the frequency or periods) per second, and c is the current. 
For reasons to be noted shortly, however, the preceding formula? are expressed thus: 

e' 
(and by substitution) l = ■ ^-. [See page 335^.) 



E = 2;rxcL, 



Taking a numerical example. Let the frequency be 50 per second, produced, 
for instance, by a AVheatstone transmitter sending 50 dots per second. In this case 
50 positive and 50 negative pulsations, that is, 50 periods per second, are being trans- 
mitted, and as each pulsation rises from zero to niaximum and falls from maximum to 
zero, there are really four variations of current in each period, or cycle (as variously 
termed), as indicated in Fig. 82^/, which represents one period or two alternations. 
Thus there are 4 x 50 = 200 variations of current in such a circuit per second. 
Suppose that in this circuit there is a relay having an inductance of one henry, and 
that the current strength is one ampere, the inductance e. m. f. e' will then be 
represented by the formula, 

I =: 20 volts. 



E =4XXCXL, 



or 



E = 200 X .1 X 



This, however, is assuming that the rise and fall of the current might be indicated 
by the uniform lines s, 5, s, s in Fig. Sid, which represent a current in which the 
increment or decrement varies at each step by a given or uniform amount.* But 
when, as in practice, the rate of variation of current is greater than this uni- 

* In this part of the subject the author follows and amplifies somewhat an article by Mr. W. J). Weaver in America)} 
ElectHcian, 2sov., 1897. Acknowledgments are also due to Mr. R. N. Inglis and Mr, Townsend Wolcott for useful sug- 
gestions hereon. 



INDUCTANCE, CAPACITY, REACTANCE, IMPEDANCE. lOOr 

form variation, it may be indicated by the curve c, which, assuming" a sinusoidal 
wave, indicates the form of curve that would result if the current or e. m. f. 
were measured at each instant of rise and fall, and which is termed a sine curve. 
If, tlierefore, it be also assumed that in varying from zero to maximum the cur- 
rent has to vary through an area represented by the quadrant n n m^ Fig. 83^^, of 
a circle, it is evident that this area of variation is greater than would be the case if 
it were limited to the area of the triangle inscribed within the quadrant by the 
straight or uniform lines. Thus there is a greater variation, four times repeated, in 
each period than is permitted by the rule defining the henry ; and this excess 

is in the ratio of — or ^^^~~ — = — , which is the ratio that the area of a 

22 I 

quadrant of a circle with a radius of unity bears to the area of the said triangle. 

(For example, x = tt x r', Avhere x is the area of a circle, with a radius r of 1, 7t 

being the ratio of circumference to diameter. Then, in numerals, .t =3. 1416 x 1"^ = 

3. 1416. The area y of a triangle whose sides r equal i is, ?/ = — =z ■ — z= .5. 

Then the area of quadrant q of the circle is ^ = ^^ = -7854, and ratio of area 

4 

q of quadrant to area y of triangle is ^ = — . J Therefore, to ascertain the 

actual inductance e. 31. f. of the circuit the result thus far obtained must be multi- 
plied by 1.5708, giving the expression 

(rt) e' = 1.5708 X 4 K X c X L, or e' = 1.5708 X (4 X 50) X .1 X I = 31.416. 

As, however, 1.5708 is one half of 3.1416, the figure 4, representing the 
variations of current per cycle, is dropped, and the formula is simplified and abbre- 
viated thus, e' = 2 7rKCL, 

which is the equivalent of formula («), for, obviously, 2x3. 1416 is equal to 4 x 1.5708. 
Hitherto in these remarks it has been assumed that the inductance of the circuit 
is known. By analyzing the preceding example the operation of the resultant or 
vector method of ascertaining the inductance, when unknown, may be utilized. 
For example, let a Wheatstone transmitter or an alternating cun-ent generator be 
arranged to send a current of . i ampere and 34. 8 volts (as measured by an alternating- 
current ammeter and voltmeter) with a frequency of 50 per second through a Morse 
relay of 150 ohms resistance. By Ohm's law, exc = e, or 150X.1 = 15 volts, which 
is the energy e. m. f. of the circuit (the component E of Fig. 82<:'). There is, then, 
in the circuit an energy e. m. f. e, of 15 volts in quadrature with the thus far un- 
known inductance e. m. f. e', the vector sum of which is 15^ + e'". To maintain 
these forces an impressed e. m. f. e, in this case 34.8 volts, is required. As the 
square of the resultant e of two such forces is equal to the sum of the squares of such 
forces, by simple equations. 

Impressed E. M. F., e'' = E^+E'% or 34.8^^ = i5^ + e'\ 

Transposing, we get, e"^ = 34-8"' — 15", or e"' = 121 1 — 225 = 986, 

Hence, as the square root of e'" is obviously e', then e' = VgS6 = 31.4 volts, 
the inductance e. m. f. of the circuit (component e' of Fig. 82^). Or, having the 
impressed E. m. f. and the inductance e. m. f., it is easy to obtain the energy or 
power E. M. F. E, for e' = 34.8' — 31.4' = 225, and E = |'2^5'= 15 volts. Thus, 
with an alternating current in a circuit with inductance, instead of simply subtract- 



100^ AMERICAN TELEGRAPHY. 

ing a counter e. m. p. from the impressed e. m. f. to obtain the energy e. m. f., as 
in the case of battery cited, the vector diiference between the impressed E. m. f. and 
inductance e. m. f. is taken. 

It is known that the E. m. f. measured by an alternating current voltmeter is 
the virtual E. m. f. and not the maximum E. M. F., and to ascertain the latter the 
virtual E. M. F. must be multiplied by 1.41. 

Impedance. — Every conductor offers a certain opposition to the flow of cur< 
rent in the shape of ohmic resistance or resistance reactance K. The reactances of 
inductance and capacity also by neutralizing more or less of the impressed e. m. f. 
virtually oppose the flow of current in a circuit, and may therefore be regarded as 
resistances. These reactances, however, act at right angles to the energy e. m. f., 
and also at right angles to the current, inasmuch as the current is in pliase with the 
energy E. m. f. Since, also, the ohmic resistance is, so to speak, in 2:)hase w^ith the 
current, it follows that the forces opposing the flow of current (ohmic resistance and 
reactance) are in quadrature with each other, and hence it is the vector sum of the 
ohmic resistance and inductance (or capacity) resistance (reactance) that is considered 
(namely, the square root of the sum of their squares), and not their arithmetical sum. 

This vector sum, or joint effect, of these reactances is tei-med impedance, z, or 
apparent resistance, and is expressed in ohms. As the apparent lesistance due to 
inductance increases directly with the inductance and frequency, the impedance of 
a circuit having only ohmic resistance and inductance resistance is expressed bj 
the formula 

z = Ve^ + {2 7n^Ly\ 

But as the apparent resistance due to capacity decreases with the increase of capacity 
and frequency, and contrariwise, the reciprocal of capacity reactance is used. Hence, 
the impedance of a circuit having ohmic resistance and capacity resistance (or con- 
densance) only, and when the capacity is in series with the ohmic resistance, is 
expressed thus: 

z = |/k^ + 



(2 7rNK)' 



The latter formula will be clear when it is considered that the larger the capacity of 
a condenser the more current will flow into it, hence the less its apparent resistance, 
or the more its apparent conductance, conductance being the reciprocal of resistance, 
and vice versa. Since further, as already remarked, inductance reactance and capac- 
ity reactance act oppositely, so to speak, on the current, when there are ohmic 
resistance, inductance and capacity in an alternating circuit, the impedance is 
thus expressed: 



= 1/ e' + ( 2 7r:sL ^ — ) . 



That is, in this case, the impedance is equal to the resultant of the resistance com- 
ponent and a component consisting of the numerical difference of the inductance 
and capacity reactances. In the above formula the inductance reactance is supposed 
to exceed the capacity reactance. When contrariwise, the inductance reactance is 
subtracted from capacity reactance. The current in an alternating current circuit 

6 

is then equal to the impressed E. :\i. f. e divided by the impedance, or - — . If the 

inductance and capacity reactances of a circuit are equal their effect upon the cur- 
rent strength is nil and the current is in phase with the impressed e. m. f. There 
is no impedance. For example, assume a circuit having capacity .000003 farads 
(3 micro-farads) and inductance 3.38 henrys, and neglecting resistance of circuit. 



PUPIN-S LOADED CONDUCTOR. 100^ 

2 7rL:N' — 2 7rxK represent inductance and capacity reactance. With a frequency 
of 50, 2;r]sr in each case will be 2x3.1416x50 = 314, and reactance will equal 

^14 X ^.^8 ,or 1061. 3 — 1061. 3 = 0. Thus, if inductance and capac- 

-^ '* ^ ^ 314 X .000003 

ity of a circuit be so distributed that this condition prevails throughout, the cur- 
rent strength would be in accordance with Ohm's law. 

A main-line Morse relay, 150 ohms resistance, with the armature adjusted for 
working, has an inductance of about 5 henrys; with the armature touching cores, 
10.5 henrys; a polarized relay, 400 ohms, with armature within .004 inch of cores, 
about 2 henrys. Kennelly gives the inductance of a bare copper wire, No. 12 
B. & S., on poles 23 feet above ground, as .003 henry per mile; a No. 6 B. & S. 
copper wire, about .029 henry per mile; a No. 9 B. & S. overhead copper wire 
has a capacity of about .01 microfarad per mile. 

Pupik's loaded C0jS"DUCT0R. — It is known that a straight conductor, such as 
an overhead telegraph line or a cable, possesses very little inductance but consider- 
able capacity, especially long cables. This tends to retardation of signals, the 
energy of the current being dissipated in charging the various parts of the cable. 
Attempts have been made to diminish the retardation due to capacity by placing 
inductance at the terminals of the cables, but as the capacity is distributed uni- 
formly throughout the length of the cable, this arrangement of inductance was not 
successful. Dr. S. P. Thompson and others have pointed out that the effective way 
to counteract the retarding effects due to uniformly distributed capacity was to 
introduce into the circuit uniformly distributed inductance; and assuming a two- 
conductor cable, he proposed to insert at intervals between the two conductors induc- 
tance coils to offset the effects due to the capacity of the cable, since inductanco 
acts oppositely to capacity. Dr. Pupin attacked the problem in a somewhat differ- 
ent way, and deduced mathematically the amount of inductance and the intervals at 
which it would be necessary to introduce inductance in series in conductors or cables 
of a given capacity, for electric wave-lengths of a given order, for instance, those 
that are utilized in telephony. This arrangement is described in U. S. patent 
No. 652,230, covering Dr. Pupin's invention, and the writer has drawn freely from the 
language of these specifications in the following description, which, however, is bub 
an abstract of the same, and for further elucidation of the subject the reader may 
be referred to the patent in question. To illustrate the principle the inventor uses 

Fig. S2e. Fig. 82/. 



the analogy of vibratmg strings, the laws of which may be found in works on physics 
In Fig. 826 a strmg is shown attached at b to the prong of a tuning-fork c and -it 
the other end to a suitable support D. If the fork is made to vibrate the strin'o- 
will make forced vibrations with it, that is, vibrations wliich follow the period 
of the tuning-fork. When the internal and external frictional resistances mav be 
neglected the waves travel with undiminished amplitude. Hence the direct wave 
coming from the tuning-fork and the reflected wave coming from d will liave the 
same amplitude, and therefore stationary waves will be formed with fixed nodes at 
aceg D, and ventral segments at b d f h. When, however, there are externaland 
internal frictional resistances the amplitude of the wave is coutinuouslv diminished 
m Its progress from B to D. After its reflection at d the returnino- wave haviu'o- ^ 
smaller amplitude than the oncoming wave, cannot form with it bV interference'^ \ 
system of stationary waves, but forms a wave curve as a' V c' cV e' f "with continuallv 



ICO/ 



AMERICAN TELEGRAPHY. 



diminishing amplitude due to attenuation, Fig. 82/, that is, a quickly damped series 
of waves. If the frictional resistance reactions are proportional to the velocity of 
propagation, the ratio of attenuation (namely, the ratio of amplitudes of two suc- 
cessive half- waves) will be a constant quantity. The velocity of propagation and 
tlie attenuation ratio depend on the density of the string, its tension, its frictional 
resistance, and frequency. For example, the greater the tension the greater the 
velocity, and consequently the greater the wave-length with a given frequency of the 
fork. Also the greater the density the slower the velocity, and heuce the shorter 
the wave-leugth with a given frequency. 

The greater the density of a string the less will be the attenuation ratio, and the 
lighter the string the greater the attenuation ratio. The energy which the string- 
receives from the tuning-fork and then transmits toward D exists partly as kinetic 
energy and partly as potential energy or energy of deformation of the string. The 
process of propagation of a wave consists in the successive transform. ation of the 
kinetic part of the total energy into potential energy, and vice versa. During this 
transformation a part of the energy is lost as heat due to frictional reactances. 
These reactions are assumed to be proportional to the velocity, so that the rate of 
loss will be proportional to the square of the velocity; but since the velocity .dimin- 
ishes with the density the heat loss is inversely proportional to the density. From 
which it is deduced that dense strings trjinsmit energy more efficiently than light 
strings, because the former require a smaller velocity in order to store up a given 
amount of kinetic energy, and smaller velocity means less dissipation into heat and 
therefore a smaller attenuation of the wave. 

Dr. Pupin then points out that the coefficient of friction, the density, and ten- 
sion of a vibrating string are an exact analogy of the ohmic resistance, the sell- 
inductance, and the reciprocal of the capacity of an electrical conductor. The mag- 
netic energy of the current corresponds to the kinetic energy of the vibrating string, 
and just as a dense string transmits mechanical energy more efficiently than does a 
light one, so a wire of large inductance per unit length will, under otherwise the 
same conditions, transmit energy in the form of electrical waves more efficiently 
than a wire with small inductance per unit length, inasmuch as a wire of large 
inductance can store up a given quantity of magnetic energy with a smaller current 
than is necessary with a wire of small inductance, hence with smaller heat losses 
and smaller attenuation and therefore with higher efficiency. 

Dr. Pupin's further experiments with a vibrating string consisted in loading it 
with beads at certain intervals, thereby adding density to the string, and he found 
that the foregoing theory was borne out. By the analogy of the beaded sti'ing it 
was also shown that if the tuning-fork vibrate at suCh a rate as to produce in the 
beaded string a vibration the wave-length of which is equal to or greater than the 
distance between B and d, the vibration of the string will then be practically the 
same as that of a uniform string of equal length, tension, frictional resistance, and 
mass. This indicated that in the transmission of electrical energy i]i long conduc- 
tors it would be feasible, by properly selecting the amount of inductance, in the shape 
of coils, and the intervals at which they should be placed, to obtain results for a 
given frequency, resistance, and capacity of conductor, similar to those in which 
the inductance is uniformly distributed in the conductor, assuming it were practica- 
ble to so distribute inductance, and this is the essential feature of Dr. Pupin's 
device, namely, that when the distance between the periodically distributed induc- 
tance is a fractional part of the wave-length of the current, the effect is equivalent 
to a uniformly distributed amount of inductance in the conductor, it being assumed, 
briefly, that when alternating currents of a certain frequency are transmitted in a 
conductor the waves are reflected back at the far end of the conductor or by a 
receiving apparatus in the system. 



THE RHEOSTAT. 



lO 



The denser the medium tne slower the rate of wave propagation in that medium, 
hence Dr. Pnpin termed his loaded conductor, consisting of inductance coils suitably 
placed, a slow-speed conductor. In working out the theory practically the inven- 
tor employs two constants, namely, the wave-length constant a and the attenuation 
constant /3. When there is no inductance in the line these may each be expressed 
by the comparatively simple formula, namely, a and /8 = i/^pKE, where k is capacity, 

2 7t 

R is resistance per mile, and /a = ^^ , where t is frequency of the impressed e. m. f. 



If X = Avave-length, then A = 



a 



The following example is given in the specifica- 



tions referred to: Suppose it is desired to transmit speech over a line 3000 miles 
overland, the wire having a resistance of 4 ohms per mile, and a capacity of .01 
microfarad i^er mile.* The total attenuation factor of a similar wire from New York 
to Chicago, about 1000 miles, is ^ ~ ^-^ for the highest frequency in speech (e being the 
base of the Naperian logarithms, 2.71828), namely, 1500 periods per second. This, 
then, must be the total attenuation factor for the 3000 mile circuit. 'J hen c"^ -^ " " ^'^ = 
the attenuation factor e^'^-'" and 3000 ^ = 1.5. Assume resistance of addrd induct- 
ance coil is .6 ohm pi3r mile, giving a total of 4.6 ohms per mile. When the 
reactance per mile is sufficiently great in comparison with the resistance as in this 
case, the following simplified formula may be used for the attenuation consta:Qt, 

^ K 

-, and from this the inductance L may be calculated as follows: 



/8 = "i 



L 



;ooo/? = 3000 



/4i = .. 



Hence L 



henry. 



Having obtained the inductance required per mile, the wave-length for the highest 
frequency used in speech, 1500 periods per second, is calculated 

, or about 15 miles approximately: 



27r 

X = — 

a 



P Vu 



1.500 



V .2 X .01 



A sufficiently high degree of approximation to a uniform telephone line will be 
obtained in this case if 15 coils of .2 henry each per wave-length, or one coil per 
mile, be employed. 

The rheostat, or resistance box. — In Fig. 83. 

testing, and in duplex telegraphy, etc., the intro- 
duction of "extra" resistance into a circuit is 
frequently necessary. For instance, in testing, 
a coil of small wire, of known resistance, is often 
used to ascertain, by comparison, the resistance 
of a wire, the resistance of which is unknown; 
and, in duplex telegraphy, coils of wire are 
used to "balance" one wire against another, 
etc. The coils of wire used for such purposes 
are generally placed together in one box, termed 
a "rheostat." It is desirable that these coils 
should not occupy much space, and for that 
reason an alloy possessing high electric resistance is usually employed in this 
capacity, most generally German silver, the resistance of which is about twelve times 
greater than copper. For purposes in which rheostats are employed, it is usually 
undesirable that the coils should produce any magnetic eftect due to the current. 




* The factor by which B has to be multiplied to get the amplitude at a given distance is termed the attenuation factor. 



I02 



AMERICAN TELEGRAPHY. 



To prevent such magnetic effect the coils in rheostats are "doubled" back 
on themselves in the manner indicated, in Fig. 83. The result is that, as the same 
current passes through parallel portions of the coils in opposite directions, as outlined 
by the arrow heads, no perceptible magnetic effect is produced; tlie explanation 
being that any tendency of the current in one portion of the coil to set up magnetic 
effects is counteracted by a current of equal strength, in the opposite direction, in the 
parallel portion of the coil. 

The coils of the rheostat are usually mounted on bobbins, and are connected up 
in the " rheostat, " practically as shown in Fig. 83 a. 

The brass plates numbered 3000, 2000, 1000, etc., are set in the ebonite cover of 
a box of suitable size to hold the coils; one terminal of a coil being connected to one 
brass plate, the other terminal to the next brass plate. The numbers indicate the re- 
sistance of the respective coils, in ohms. 

FIG. 83 a. 




The brass plates have semi-circular openings cut in them into which metal plugs 
p, Fig. 83, and a, b, c. Fig. 83 a, can be inserted to connect any two brass plates for the 
purpose of " short circuiting " any coil whose terminals come to the i)articular jDlates 
into which a plug may be inserted. Thus, when the brass plates are connected by 
plugs, as at A, B, c, in the figure, the 2000, 1000 and 500 ohm coils are short-cir- 
cuited out of circuit; that is, those coils will not be traversed by a current passing 
through the other coils because of the very low resistance of the metal plugs, as com- 
pared with the resistance of the coils, which low resistance of the plugs practically di- 
verts all current from the coils short-circuited thereby. 

By thus inserting or removing the plugs, obriously, more or less resistance can be 
inserted or withdrawn from a circuit at will. 

Other forms of rheostats will be found described in chapters on Wheatstone 
bridge, the Wheatstone automatic system, the Quadruplex, etc. 



CHAPTER VII. 



GALYAXOMETERS, VOLTMETERS, AMMETERS. 

In the electrical tests required in practical telegraphy the instrument chiefly used 
is the galvanometer. 

The term galvanometer, as the word implies, signifies an instrument for ''meas- 
uring" electricity. The galvanoscope is an instrument designed to indicate merely 
the presence of electricity in a substance. In many of the tests necessary in teleo-- 
raphy the galvanometer is used as a galvanoscope, or "indicator" of the presence of 
an electric current, and only rarely as a direct means of measuring the strength 
of current, but the results obtained are, nevertheless, indirectly due to the fact that 
the current is, so to speak, measured, as may be evident from the ensuing descrip 
tions of certain forms of galvanometers. 

The galvanometers mostly used in telegraphy are the tangent galvanometer, 

Fic:. 8i. 



^A- 



3IIIIIIinHiiiimiino=»-j) 



the "detector/' and Thomson reflecting galvanometer. 

Theory.— It has been established that the earth is a magnet, having north and 
south "poles," between which magnetic "'lines of force" are constantly passing. A 
magnetic needle freely suspended tends to point north and south because of the di- 
rective influence of the earth's magnetic lines of force; in other words, because the 
magnetic lines of force of the needle seek to obey the tendency of magnetic lines of 
force to coincide in direction. When in this position, namely, pointing north and 
south, the needle is said to be in the magnetic meridian. 

When a magnetic needle is held parallel to a wire conveying an electric cur- 
rent the needle will be deflected. This deflection of the needle is due to the action 
of the magnetic lines of force, which, as stated more fully elsewhere, (Chap. III.) 
surround a wire in which an electric current is flowing. The direction of the de- 
flection of the needle depends on the direction of the current in the wire. For ex- 
ample, assuming the needle to be freely suspended above the wire, as in Fig. ^4, it 
the current in the wire be flowing towards the north pole of the needle, the south 

\o3 



I04 



AMERICAN TELEGRAPHY. 



pole will be deflected to the right of the wire. If the current be flowing toward 
the south pole of the needle the north pole will be deflected to the right of the wire. 
If the needle be placed beneath the wire the deflections will be in the reverse direc- 
tions. The extent, or angle, of deviation of the needle will vary with the strength 
of current in the wire, but except for very small deflections will not be proportional 
thereto; which remark will be amplified later on. 

Upon this action of the needle in the presence of a wire in which a current is flow- 
ing the operation of the galvanometer is based. As, however, the effect due to a 
single wire would produce a very limited deflection of the magnetic needle, unless 
the current in the wire were quite strong, or the needle very sensitive, or both, it is 
customary, in the construction of ordinary galvanometers, to arrange the wire in the 
form of a coil, or ring, of many convolutions, in the center of which the needle is 
suspended. By this means the effect is multiplied manifold and galvanometersi capa- 
ble of responding to very minute currents in the coil are thus obtained. 

FIG. 85. 

B D 




If the earth's magnetic influence upon a magnetic needle should be temporarily 
eliminated while the needle is at the center of a coil of wire carrying an electric 
current, what has been said relative to the effect of the earth's magnetic influence 
upon the needle would be true of the effect of the magnetic influence of the coil, 
namely, the needle would tend so to turn that its magnetic lines of force, and those 
of the coil, would be alike in direction, and, consequently, it would turn at a right 
angle to the plane of the coil. But the earth's magnetic influence upon the needle is 
not eliminated, except under sj^ecial conditions to be referred to later. This being 
so, when a magnetic needle is so placed within a coil of wire that the earth's mag- 
netic force tends to jDoint it north and south, while that of the coil tends to point it 
east and west, it will point neither due north nor due west, but will, in fact, assume 
a position between those points. 

In mechanics, when two or more forces act upon a point, the combined effect of 
those forces is termed the resultajit force, and the forces thus jDroducing that result- 
ant are termed its componeiits. Analogously, it has been found that the position 
which a magnetic needle will assume, when placed as stated, will be that due to a 
resultant force composed of the two magnetic forces. 

THE TANGENT GALVANOMETEE. 

The tangent galvanometer depends for its operation as a current meter on the 
law that the currents which may flow in its coil, or coils, are proportional to the tan- 



G ALV ANO M ETE RS. 



105 



rents of the angles of deflection of 



FIG. 86. 



the needle due to those currents. This law, it 
will be found, is derived, primarily, from a knowledge of the fact that the deflection 
of the needle is due to the resultant force of the earth's and the coil's magnetic 
forces. 

The resultant of two such forces as those referred to can be graphically indi- 
cated by a diagram such as is shown in Fig. 85, which illustrates what is termed 
the parallelogram of forces; the principle of which may be stated as follows: If 
from the point /, on which two forces are assumedly acting, the lines a c, a b, be drawn, 
representing the direction and magnitude of the respective forces, and, from those 
lines, as sides, two other lines, c d and b d, be drawn, to complete the parallelogram, 
then a diagonal d, from a to d, will represent, in direction and magnitude, the re- 
sultant of the two forces. This statement may be illustrated by the following well- 
known mechanical experiment. In Fig. 86 let the weights .rj's be suspended, as indi- 
cated, by light, flexible cords; the cords attached to x z being passed over small pul- 
leys in such a manner that friction may be neglected. The three weights, or forces, 
are then acting upon the point p, and the weights come to rest in a position where x 

z exactly counterbalance y. In the actual ex- 
periment a slate, or black-board is usually placed 
immediately behind this arrangement of the 
weights, cords and pulleys so that the direction 
of the cords may be readily traced. The line a b' 
will then represent the direction in which the force 
X is acting; the line ac', that in which z is acting, 
and the line a a', that in which the force y is 
acting. Divide a portion a c, of the line a c' into 
as many units of length as there are units of 
weight in z, and a portion, a b, of a b' into as many 
units of length as there are units of weight in 
X, and complete the parallelogram a b d c, 
by drawing the lines c d; b d. Then, accord, 
ing to the principle of the parallelogram of forces, the diagonal d is the resultant of 
the forces x and z, and, as this resultant force is, in strength, equal to, and, in direc- 
tion, opposite to the force ;•, the diagonal d should contain as many units of length 
as there are units of weight in V, which will be found to be the case. Should the 
weights X or z be varied, the diagona\, or resultant, will also vary, but whenever equil- 
ibrium is obtained it will be found that the diagonal will always represent in magni- 
tude and direction the resultant force. It may also be noted, in connection with the 
application of this principle to the case in point, that it will be found, that the length 
of the line d b, taken from the point of intersection with the diagonal, will also be 
a measure of the magnitude of the force which that line represents; the line p b, it 
is understood, being, in length, equal to tlie side c a, of the parallelogram. In Fig. 
87 several such parallelograms are shown. 

The two forces now to be considered are those due to the earth's magnetic field, 
and the magnetic field of the coil, and the object, or point assumed to be acted 
upon, is that of the end of a short magnetic needle, pivoted at p, at the center of 




io6 



AMERICAN TELEGRAPHY. 



a coil, or ring of wire. The needle is assumed to be, normally, in the magnetic meri- 
dian ba', and in the plane of the coil. 

As it may be taken for granted that, in the space about the needle, the earth's 
magnetic field does not vary in strength, that strength may be called i. The direc- 
tion in which that strength is exerted on the needle may then be indicated by the 
line A B, and the strength, that is, the magnitude, i, may also be indicated by th^ 
same line. The strength of the magnetic field of a coil, however, in the space about 
the needle, may be varied as desired, but we may begin by calling it i also. As 
tlie force of that field is exerted at right angles to A p., its direction may be repre- 
sented by the line AC. A parallelogram a b c d may now be finished by drawing, 
ill accordance with the foregoing stated rule, the lines c d, and D B, as sides. The 



FIG. 87. 




3JO' 



resultant of the two forces, each having a strength of i, will then be represented 
by the diagonal a d, and, since this diagonal represents, in direction and magnitude, 
the resultant of the two forces a b, ac, a needle acted upon by two such forces would be 
deflected to a position, or an angle, coincident with the resultant line a d. 

If, now, the strength of the magnetic field of the coil be increased three-fold, 
its strength will be indicated in the figure by the line a c' The strength of the 
earth's magnetic force remaining as before, namely, i, a new parallelogram is finished 
by the lines c' d' and d' d, and the resultant force will be rej^resented by the diag- 
onal A d' ; and a needle acted on by two such forces would be deflected to a position 
coincident with that resultant. 

A means of ascertaiiiing the resultant force due to the earth's and coil's mag- 
netic forces is then afforded by a knowledge of the fact that a magnetic needle will 
be deflected to a position, or angle, coincident with the diagonal representing the re- 
sultant of the component forces For example, if it is found that a magnetic needle, 
capable of describing a circle having a radius equal to the line ab, is deflected to an 



GALVANOMETERS. 



107 



angle of, say, 71°, {see Fig. 87,) we know that the diagonals will represent the resultant 
of the two magnetic forces producing the deflection. 

We have seen that a diagonal touching the line b d' at the point 3, Fig. 87, rep- 
resents the resultant force of a magnetic force of 3 acting against a magnetic force 
of I, on the needle p. We may see further that a magnetic force, due to the coil, 
which would cause a deviation of the needle, against the magnetic force of the earth, 
to an angle, or degree, where a line continued therefrom would touch the line b d', at 
2, would have a strength of 2; and that a magnetic force due to the coil of 2\, 
similarly acting against the magnetic force of the earth, would deflect the needle to 
an angle where the diagonal E would touch the line b d', midway between 2 and 3, 
namely, at 2.5, etc., the line b d' lengthening, or shortening, directly as the strength 
of the magnetic force of the coil is increased or decreased. It thus follows, from 




what has been said, that the length of the lineBD', reckoned from b, Fig. 87, to 
the point where it may be touched by a diagonal, or resultant line, \% directly pro- 
portional to the strength of the coil's magnetic force. Further, as the magnetic force, 
or field, of a coil, surrounded by air, is proportional to the strength 
of the current flowing in it, it also follows that the strength of current in such a S)il 
Avill also be proportional to a line similar to b d. For example, if a current of i am- 
pere in the coil should originate a magnetic force at the needle, suflicient, when 
acting against the earth's magnetic force, to produce a resultant force, repre- 
sented by the line a d, (Fig. 87,) then a current of 3 amperes will be required to origi- 
nate that magnetic force which, also acting against the earth's magnetic force, causes 
a resultant represented by line a d'. 

Assuming a circle with a radius a, to be drawn around p, Fig. 88, a straight 
line, such as T, (which corresponds to line b d, or b d' in Fig. 87,) drawn from a point 
o on a circle, but not cutting it, is termed a tanoe?tt', and a line drawn from/;, throuo>h 
any degree of the circle, less than 90°, will touch a tangent at a point which ''is 
termed the /^;7-^;z/ of the angle. For example, the tangent of the angle of 45° is, 
m this case, o i; that is, the line o i is the tangent of the angle p o o'. ""Analoo-ously' 
the tangent of the angle of 71° is 03, etc. In referring to th^e anole of deflection of a 
magnetic needle, its tangent is termed the " tangent of the angle of deflection." The 
tangent in this case, may, for the purpose of illustration, be^ said to correspond to 



io8 



AMERICAN TELEGRAPHY. 



one of those sides of the parallelograms which represents the magnetic force due to 
the coil. Since, then, the " tangents " of the angles of deflection of the needle with- 
in a coil of wire, may be shown to be proportional to the strength of the currents in 
the coil the converse law is deduced, that such currents are directly proportional to 
the " tangents of the angles of deflection of the needle. " This law, however, only 
holds when the needle of the galvanometer is acted on by the two forces uniformly at 
all points ; which will only be the case when the lines of force of the coil are of sufli- 
cient length in a straight line tb furnish a practically uniform field around the needle, 
regardless of the position it may assume. 



FIG. 89. 



Fig. 89 may be considered as representing the earth's magnetic lines of force; 
for while, taken as a whole, those lines of force are curved lines, any portion of them, 
of the length of an ordinary magnetic needle, is so slightly curved as to be practi- 
cally straight. Hence, the earth's lines of force, in the vicinity of such a needle, 
may be considered as being of uniform direction and strength, and it only remains to 
insure that the magnetic lines of the coil shall also be practically uniform in direc- 
tion in that portion of the field where the needle is placed, in ord.er to secure the 
essentials necessary to the successful operation of the law referred to. 

We have seen, (Chap. Ill) that a wire carrying a current is surrounded by mag- 
netic lines of force, in concentric circles. 



FIG. 90. 




"When wires conveying a current are i3laced parallel with each other, if the current 
in each Avire is in opposite directions there is found to be repulsion between the 
"lines" of the respective wires, which may be represented as in Fig. 90. When the 
current is in similar directions in the respective wires there is found to be attrac- 
tion between the lines of force, which then tend to coalesce and form larger circles, 
as outlined in Fig. ^i . These actions are virtually similar to those of the poles of 



GALVANOMETERS. 



09 



magnets, which, when "unlike," attract each other, and, when "like," repel each 
other; the attraction and repulsion being due to the tendency of the lines to coin- 
cide in direction ; this very tendency in the case of like poles, as stated, apparently 
producing repulsion. 

When a wire carrying a current is formed into a ring, or circular coil, it is evi- 
dent that at any two opposite parts of that ring the current will be Howing in oppo- 
site directions, and hence, the form of the lines of force within such a coll may bein- 

FIG. 91. 




dicated as in Fig. 92. In that figure c c'are sections of a circular coil of wire taken 
at diametricall}^ opposite points. The space within the dotted lines / may represent 

FIG. 92, 




the plane of the coil, the small dots a section of the earth's lines of force, and the curv- 
ed lines the lines of force that emanate from the coil. Similar curved lines mav be 



no 



AMERICAN TELEGRAPHY. 



assumed to emanate from every other part of the coil. It is seen in Fig. 92 that the 
lines nearest the coil have a sharper curve than those more remote therefrom, and that 
those lines near the center of the coil are nearly parallel. Hence, if a magnetic needle 
be placed in the center of the coil, as at x, it will be in that portion of the Held of the 
coil where the lines are most uniform and, if the needle employed be a very short one 
in comparison with the diameter of the coil, it may be moved to a position of right angles 
to the plane of the coil, (as shown in the figure; an angular deflection not obtained in 
practice, without emerging, very materially, from the uniform field. In constructing 
a galvanometer, therefore, which is intended to avail of the law that the currents 
flowing in a coil are proportional to the tangents of the angles of deflections of the 
needle, a needle whose length is from six to eight times less than the diameter of the 
coil, is generally used, which ratio is found to be quite sufiicient for practical work. 

A form of tangent galvanometer much used in tele- 
FiG. 93. graphy is shown, theoretically, in Fig. 93. It consists 

of coils of insulated wire, forming a circle, at the center 
of which a very short magnetic needle is freely sus- 
pended. One of the coils of the wire surrounding the 
needle consists of a ribbon, or band of copper ; the other 
convolutions are wound and connected as shown. In 
order to obtain a variable effect upon the needle, as 
maybe required, the convolutions are *• tapped'' at 
various points and led to the metallic discs marked 
o, I, 10, 50 and 200. If, for instance, it is desired to 
place in circuit all of the convolutions, a metallic 
plug is inserted between the brass plate p and the 
disc marked 200. All the other discs on the left hand 
side are left disconnected. If it is desired to use only 
the copper ribbon, the plug is inserted at the disc 
marked o. If it is desired to include the convolutions 
o, I and 10 the plug is inserted as shown in Fig. 93. 
It is sometimes desirable to be able to reduce the 
deflection of the needle without altering the electro- 
This may be done by placing in the galvanometer cir- 
cuit one or more of the resistance coils r r, which may be short-circuited by metal ]flugs, 
in the usual way. In the figure the 5000 and 500 ohm coils are short-circuited and 
the lo-ohmcoil is in circuit. The external wires are connected to biudino^ screws b, b. 




TANGENT GALVANOMETER (THEORY.) 

motive force of the batterv. 



Westeex rxiON tangent galvano:«:eter. — This form of tangent galvanometer, 
as constructed for service, is illustrated in Fig. 94. It is known as the Western 
Union Standard. The coils of wire of the galvanometer are contained in the vertical, 
circular, gi'ooved frame R. This frame is about six inches in diameter. The resist- 
ance spools are enclosed in a circular box. under the base of the instrument; the base 
is composed of hard rubber. The instrument is supported on three adjustable legs, 
by means of which it is levelled. The needle is balanced on a jewelled pivot; some- 



GALVANOMETERS. 



Ill 



times it is suspended from tli3 arch of the coil or other suitable point. The length 
of the needle is | iuch. 

As it would be inconvenient to read deflections from the needle itself, owing to 
the small circle which it would describe, there is fastened to it, at right angles, a long, 
light pointer of some non-magnetic material, such as aluminum, the ends of which ex- 
tend to curved scales on the circumference of a dial placed immediately beneath the 
ends of the pointer. Any deflection of the needle deflects the pointer to an equal 
angle. On one half of the dial the degrees of a circle up to 90^, on each side of a 
zero, are marked. When normally at rest, the needle, being then under the directive 
influence of the earth's magnetism only, points north and south. When current is not 
flowing in the coil it is turned so as to be 

directly in line with the needle. Con- ^^^ 

sequently, the pointer at such times will ^..agg- ^ ^-^-b ^^ R 

lie at right angles to the plane of the 
coil, and its ends will be over the zeros 
of the scales. When current is caus- 
ed to flow in the coil the needle is 
deflected and the extent of this deflec- 
tion is shown in degrees by the pointer. 



Table of tangents. — If the strength 
of currents flowing in the coil were 
directly proportionate to the angles of 
deflection of the needle we would know 
that if a given current deflected the 
needle to, say, 20°, a current which 
would deflect it to 40^ would be of 
double the strength of the first cur- 
rent. But, as such is not ' the case, 
it is necessary, in using the tangent 
galvanometer, first to note the degrees 
of deflection of the needle, and then 
ascertain the tangent of the angle of the 
deflection. 

To facilitate finding these tangents, a table of tangents, similar to that giveji at 
the end of this chapter, is usually employed. In this table it is assumed that the 
tangent of the angle of 45° is unity, or i, and that the tangential line is di^'ided into 
any number of divisions of equal length. For instance, the tangent of 45°, in Fig. 
ZZ, being I, tangent 2 represents a space on the line from i, equal to that which 1 rep- 
resents from oto I, and so on. These divisions are assumed to be divided again into 
100 or 1000 parts. Thus, by reference to the table it is found that the tangent of 20° 
is 0.364, that is, {^-^^ of i. 

These tables are then used in the following way : 

For example, assume that the needle is deflected by a given current to an angle 
of 20°, and that a different current deflects it to an angle of 36°. V>\ reference to the 




W. U, TANGENT GALVANOME-IER. 



112 



AMERICAN TELEGRAPHY 



table of tangents it is found that tlie tangent of 20° is 0=364 and the tangent of 36*^, 
0.728. As the currents in question are proportional to these tangents it is evident 
that the last curient has twice the strength of the first, since c.364 is to 0.728 as 1 
is to 2. 

Knowing this law, then, and utilizing it in connection with Ohm's law, it is 
quite easy to avail of it in testing. For instance, if, with a given electromotive force 
and a given resistance in a circuit, a deflection of 36° is obtained, and with the same 
electromotive force, but a different resistance, 20° is obtained, we conclude that this 
last resistance is just double that of the former. For, as we have just seen, since the 
tangent of 20° is .364, namely, half that of the tangent of the angle of 36°, which is .728, 
it follows that the current strength must have been halved to cause the diminished 
deflection, and, by Ohm's law, it is known that with a constant electromotive force, 
the halving of the current strength in a circuit must be due to a doubling of the re- 
sistance, etc. 

In some forms of tangent galvanometers one-half 
of the circumference of the dial is allotted to a scale 
on which the tangent of the angle, instead of the de- 
gree of the angle, is marked. This avoids reference 
to a table in calculating results, and when rough 
results only are desired it is a convenient arrangement 
but when greater accuracy is required the table should 
be referred to. 

ASTATIC GALVANOMETERS. 



FIG. 95. 




ASTATIC GALVANOMETER. 



In order to eliminate as much as desired the effect 
of the earth's magnetic influence upon the needle of a 
galvanometer, and thereby to make it more sensitive 
to the magnetic influence of the coil, at least, two de- 
vices have been employed. One of them consists of 
placing a ''j^ermanent " magnet sufficiently close to the 
needle and in such a position that the earth's mag- 
netism is practically neutralized. In fact, it may not 
only be entirely neutralized, but, in addition, the per- 
manent magnet may be caused to act as the directing force of the needle. Examples 
of this device are given in the description of the Thomson reflecting galvanometer, 
although it is also applied to other forms of galvanometer. The term '^ permanent'' 
is applied to those magnets in which the magnetism is not maintained by an electric 
current. The common horse-shoe magnet is an example of this class. The metal of 
permanent magnets is usually hardened steel. 

Another device for eliminating the effect of the earth's directive influence consists 
of the use of two magnetic needles, one above the other, supported at their centres on 
a common shaft. Fig. 95. 

As it is difficult to make the needles equal in every respect, one of them will gen- 
erallv be slightly stronger than the other, or it may bemiide so purposely. The needles 



GALVANOMETERS. 



II 



FIG. 96. 



are placed parallel with each other, the north pole of one being placed directly above 
the south pole of the other and vice versa; the consequence of which arrangement is 
that the tendency of one needle to point north is counteracted by that of the other to 
point south, with the result that the slightly stronger needle controls the direction of, 
but leaves the pair in a very unstable position, and one from which it will be very 
readily deflected by any external magnetic influence. 

Such an arrangement of the needles is termed an astatic, or unstable, arrangement, 
that is, virtually, one m which the needles are indifferent to the position in which they 
may be placed. 

This astatic arrangement is used extensively in 
galvanometers of the Thomson reflecting pattern. 
It is also used in a form of galvanometer called 
the detector, which is employed for testing pur- 
poses quite extensively in telegraphy. It may be 
jnade quite sensitive, and is useful in ordinary 
testing where a Thompson reflecting galvanometer 
might be too sensitive, and the ordinary tangent 
galvanometer not quite sensitive enough. It is 
used frequently in Wheatstone bridge testing, 
where it indicates the passage of current through 
the bridge wire. 

Dei ectoe galvanometer. — A ] )etector galvano- 
meter is shown with a section cut away for illustra- 
tion, in Pig. 95. One of the needles of the astatic 
system is placed within the coil, the other above 
it. The upper needle carries a pointer, one end of 
which traverses a short scale, not shown in Fig. 95, 
The needles are suspended by a silk fibre from the 
top of the glass case, within which the galvanometer 
is enclosed. 

In addition to the sensitiveness secured by the astatic arrangement of the needles, 
an additional advantage accrues from the placing of the needle within and above the 
coil, namely, that a greater deflecting force is exerted on the united needles than would 
be the case with a single needle, inasmuch as the lines of force acting on the lower 
needle, and those acting on the upper needle, both tend to turn the arrangement, as a 
whole, in the same direction. This remark may become clear by considering that, if 
a needle be placed above the coil and, looked at from above, should be turned to the 
right by a given current, the same needle, if placed below the coil, with the position 
of its poles reversed, would still be deflected to the rio-ht. 

A form of the " detector " galvanometer used in practice, is shown in Fig. 96. It is 
placed on a tripod, with a ball and socket joint, to permit a ready leveling of the in- 
strument. Small magnifying glasses are placed on the top of the case in order to 
assist in detecting slight movements of the needle. A device is also provided 




DETECTOR GALVANOMETER. 



114 



AMERICAN TELEGRAPHY 



for holding up the needles when not in use, thus taking the strain off the silk fibre. 
It will be understood from what has been said that the deflection of an instru- 
ment such as the " detector,'' is not proportional to the current traversing the coils, ex- 
cept for very small defl.ections, especially as the needles are generally much longer than 
tlie needle of the tangent galvanometer and, consequently, soon pass out of the m.ore 
uniform field of the coils. 

The scale over which the pointer moves 
^^^- 97- is provided chiefly to enable a "reading'' 

to be taken when comparative results 
only are required. Of conrse, a given 
current passing through the coil will 
deflect the needles a given distance 
and, therefore, it would be quite prac- 
ticable to calibrate the scale so that the 
instrument would act as an ampere meter, 
that is, a measurer of current strength. 

The differential g.axvaxometer. 
The differential galvanometer was at 
one time in extensive use in telegraph 
testing in this country, but of recent 
years it has been replaced for that pur- 
pose by other forms of galvanometers. 

It is now mostly used as a " tell tale,'* 
in Wheatstone automatic telegraphy. 

In brief, tlie differential galvanometer 
is, in principle, similar to a differential 
relay, {See Duplex Telegraphy,) a mag- 
netic needle pivoted at its centre re- 
placing the armature of the relay. 




THOMSON REFLECTING GALVANOMETER. 



THE THOMSON REFLECTING GALVANO- 
METER. 



This well known instrument is mainly used, in telegraphy, in the electrician's de- 
partment, in tests of the resistance of insulating materials, insulated wires, cables, etc; 
electromotive force and internal resistance of batteries; electro -static capacity of 
cables; conductivity of wire, etc., the great sensitiveness of the instrument rendering 
its use for testing wires parallel with " live " wires somewhat unreliable. The instru- 
ment is also used as a "reading" galvanometer in submarine cable working, as ~ 
described in Chapter on Submarine Telegraphy. 

In the construction of the Thomson reflecting galvanometer, as a rule, four coils, 
wound on bobbins, are employed, which coils are placed in pairs, one pair above the 
other, and are supported by suitable frame-work, as in Fig. 9 7, where a a' are the up 



Gy\LVANO METERS. II5 

per coils and b b' are the lower coils, as seen sidewise; a section of the coils and frame 
being removed, in the drawing, for tlie purpose of illustration. The four coils may be 
readily connected together in series, or in multiple. Two magnetic ncdles are usually 
employed, one placed at the center of the two upper coils, as shown at x, the other at 
the center of the two lower coils, as at x' in the figure. 

The needles are supported by a thin aluminum wire shaft a, shown more clearly 
m Fig. 98, forming, virtually as in the case of the "detector" galvanometer, an astatic 
needle system. Each "needle " is really formed of a number of small needles strongly 
magnetized, generally made out of watch spring. In the case of the upper needle 
these small magnets are attached to the back of a small, circular mirror, \ or 1 of an 
inch in diamieter, which is itself carried by the aluminum wire. The lower needle is also 
attached to the aluminum. A vane of light material, such as mica, is often placed at 
right angles to the needles for the pur])Ose of retarding their swing. 
The needle system is upheld by a fine cocoon silk fibre attached to a mov- 
able pin p which fits into a slot in tlie top of the framework supporting ^^'^' '^^• 
the coils. The coils, needles, and their supports, are contained within a glass 
or brass case. Above the coils and outside of this frame, a curved magnet m 
is supported by and movable upon a rod r. This is termed a directing mag- 
net, the utility of which will be mentioned later on. In some portable forms 
of the instrument the two lower coils are dispensed with and only the two 
upper coils are used. 

The manner in which one form of the Thomsom reflecting galvanometer 
is set up for use is shown in Fig. 99. The form there shown is the tripod. 
In the figure,L is a lamp, s a scale and s' a set of " shunts,'' or resistances 
These shunts are used to divert certain portions of the current from the gal- 
vanometer coils in cases where, with the full current passing in the coils, 
the deflection would exceed the dimensions of the scale, or when, for any 
reason, a diminished deflection may be desired. i^See end of section.) 
The object of the lamp and scale will presently be seen. A slit is made in the 
board below the scale s. The lamp is placed behind this slit and its beams fall 
upon the mirror n of the galvanometer, and are reflected back on the scale. Any de- 
flection of the needle thus causes the reflected beam of light to traverse the scale to the 
right or left, according to the direction of the deflection of the needle. The scale is 
usually about 18 inches in length, and is divided into 720 divisions; that is, into 360 
divisions each side of the zero, which is placed directly above the slit. 

The scale may be considered as representing the tangent of the angles of 'deflec- 
tion of the needle. For example, if the needle be deflected so that the beam is re- 
flected on the scale as indicated in Fig. 100, it will be seen that the beam reaches the 
scale a.t a point where it would be intersected by a tangent t, drawn from the semi-cir- 
cle c at zero. Thus, by the use of this ingenious instrument, the practical equivalent 
of a pointer without weight, reaching from the needle to the tangent line, is obtained, 
and also one which, by its length, gives a considerable deflection with a scarcely per- 
ceptible motion of the needle, and a comparatively large deflection with an exceedingly 
feeble current. 

Apart, also, from the fact that the scale line becomes, virtually, the equivalent of 



ii6 



AMERICAN TELEGRAPHY. 



the tangent of the angles of deflection of the needle, it is to be noted that with the 
needle at some distance, say 3 feet from the scale, a deflection of the needle of but 7^, 
would cause the reflected beam to traverse the scale to its limit, assuming the beam to 
have started from zero, as may be seen by an examination of Fig. 100. Therefore, if 
as, perhaps, is more frequently than otherwise the case in practice, the deflections do 
not exceed 50 or 100 divisions of the scale, it would be equal to working with deflec- 
tions of 1° or 2° on an ordinary tangent galvanometer; in which case the currents 
would be, for practical purposes, proportional to the angles oi deflection, so slightwould 
be the variation between the angle and the tangent of the angle. 



FIG. 99. 





Since the scale line may be said to correspond to a tangent of the angle of de- 
flection of the needle, it will be observed that the strength of current in the coil of 
the Thomson reflecting galvanometer will be proportional to the deflection of the 
needle as indicated on the scale. This deflection is not, however, strictly proportional 
to tlie current in the coil of the oralvanometer, owino* to the fact that the ano-le of de- 
flection of the beam is double that of the actual angle of deflection of the needle. 
This may be understood, or verified, by observing that a hand-mirror, when held 
towards -the sun at an angle of, say, 45 degrees, will cast a beam at a right angle, or 
90°, to the direction in which the rays strike the mirror. But the variation due to 
this cause for very small deflections of the needle is not great, and even for larger 
deflections, imless where the strictest accuracy is required, it may be neglected, and 
the calculations made from the results of the actual reading of the scale. 

Galvanometer shunts. — The resistance of the coils of the Thomson reflecting 
galvanometer varies in different instruments, and with the purpose for which each 
instrument is designed, ranging from 5,000 to 50,000, or more, ohms, in instruments 
intended for measuring high resistances, to less than 2 ohms in instruments intended 
for measuring very low resistances. For example, certain ordinary instruments of 



GALVANOMETERS. JI7 

the former class, will give i division deflection with a current due to i volt through 
100,000,000 ohms; that is, with a current of ioqooo,ooo ^^ ^^ ampere; while instru- 
ments of the latter class will give perceptible deflections due to variations in the 
current strength, caused by minute variations in the length of the conductor under 
test, or by the minute variations of temperature of the wire caused by the momentary 
contact of the hand of the operator with the wire. Owing to this sensitiveness of the 
instrument it is essential, in order to enlarge its range of measurements, that means 
be provided for diverting certain portions of the current from the instrument; other- 
wise the limit of the scale would soon be reached. In practice the means used for 
this purpose are coils of wire termed " shunts, " one of which, at a time, is placed 
across the terminals of the galvanometer coil; thereby forming with the latter a 
* divided" circuit. It is thus obvious that the current which will flow in the re- 
spective branches of this divided circuit will be proportionate to the resistance of 
each branch, and may be calculated accordingly, 

FIG. TOO. 



r '.,; .^- 

L si ' 

:* ^ 1 

The "shunts " generally consist of three coils, termed the ^ shuut, the -^^ shunt 
and the -q^ shunt. The resistance of each coil is arranged to bear a definite rela- 
tion to the total resistance of the galvanometer coils, so that when, for instance, the 
galvanometer is shunted with the coil of the lowest resistance, namely, the -^^ shunt, 
^ 1 0^0 P^i't of the current flows in the galvanometer, the other two P^^i'ts flowing 
through the shunt. When the -^ shunt is used a y^^ part of the current flows through 
the galvanometer, the other -fj^^ parts flowing through the shunt, and when the ^- shunt, 
namely, the shunt of highest resistance is used a -^jj part of the current flows in 
the galvanometer coil, the other -^^ parts in the shunt. Consequently, any deflection 
obtained when the ^ shunt is used is multiplied 10 times, for the reason that, were 
the shunt not used, the current flowing in the galvanometer coils would be 10 times 
strongtT and thus would deflect the needle to an angle whose tangent would be 



ii8 



AMERICAN TELEGRAPHY, 



FIG. lOI. 




practically lo times greater than that of the angle obtained when that shunt is used. 
Similarly, when the -^ shunt is employed, the deflection is multiplied loo times, and 
when the -g^ shunt is employed, looo times. On this account the various shunts 
are sometimes termed the tenth, hundredth and one thousandth shunts. 

Without this arrangement of shunts the usefulness of the galvanometer would be 
much reduced, since, as stated, by its aid many measurements may be made which other, 
wise would be impracticable. This is especially the case where measurements by the 
*' direct deflection, " or "substitution,", method of measuring high resistances, is con- 
cerned, for, without shunts of known multiplying powers, it would be necessary to 
utilize known resistances of a value equal to the resistances measured, which would 
be far in excess of those now employed or required. 

A form of ''shunts" much used 
with the Thomson reflecting galvan- 
ometer is outlined in Fig. loi. a 
B c D E are brass segments and f is a 
brass disc. s s are binding screws 
to which the wires leading to the 
galvanometer etc., are attached. 
(In practice the disc F is connected 
by wire to segment e, under the disc, 
but, for clearness, it is shown con- 
nected on the top, in the figure.) The 
•^ shunt coil is connected by one of 
its terminals to a, and, by the other, 
to B. The Q^g- coil is also connected 
to A, and, by its other terminal, to c, 
and similar terminals of the -g^g- 
coil are connected to a and to d. 
When a plug is inserted in the aper- 
ture a the current diverted through 
the sliunt follows the path from s, 
through the -J- shunt to rand s', or 
contrariwise,and the insertion of a 
plug at y, or at a'' brings into operation either the ^\ or the -^ shunt. Only one 
coil is supposed to be inserted at a time. It is seen that the coils are always open 
at one end except when connected in by a plug at ^, ^, ' or ^". The galvanometer 
maybe short-circuited by inserting a plug at e. The shunt coils are " double " 
wound, as in the case of the ordinary rheostat. 

When it is desired to obtain a multij^lier different from any in the regular 
shunt the coils of an ordinary rheostat may be utilized, and the amount of resistance 
necessary for a given multiplier may be found by the formula : — 



GALVANOMETER SHUNTS (THEORY.) 



where k is resistance of the galvanometer coils, and m the multiplynig power of shunt 



GALVANOMETERS. II9 

desired. For example, if the resistance of galvanometer be 4000 ohms, and a shunt 
for a m.altiplier of 40 be desired, the resistance necessary to place in the shunt will be 

-''■ ; that is 102.56 ohms. 

40 — 1 

DiiiECTiNG MAGNET. — The Thomsou reflecting galvanometer is generally set up 
with its needle or needles pointing north and south, and in this position the direct- 
ing magnet may be raised on its supporting rod to a maximum height from the 
needle. It is not, however, absolutely essential that the needle should point north 
and south, since, by lowering the directing magnet, it, as it were, assumes control of 
the needle and by its use the latter may be caused to point to zero of the scale in 
almost any position. The sensitiveness of the galvanometer is, however, reduced 
when the magnet is in very active control of the needle. The closer the directing mag- 
net is brought to the needle the more quickly does it resume its position of zero after 
the deflecting cause has been removed. It is often beneficial, indeed necessary, by 
the use of this device, to waive some of the sensitiveness of the instrument 
when external changes of magnetism, or the movement of iron in the vicinity, would 
tend to disturb the needle if directed chiefly by the earth's magnetism. 

In testing with this galvanometer care should be taken not to carry knives, mag- 
netized watches, etc., on the person, as erroneous results may be caused thereby. It 
is very important that the needles of the instrument should be perfectly level. 

The form of instrument shown in Fig. 97 is always equipped with a spirit level. 
The tripod form may be levelled by a pocket spirit level. 

Further allusion to this galvanometer will be found in connection with chapter 
on cable testing. 



THE d'ARSON^YAL REFLECTING GALVANOMETER. 

This galvanometer differs from the Thomson (now Kelvin) reflecting galva- 
nometer in that it employs a movable coil in a magnetic field, practically similar to the 

siphon recorder (page 269). The coil 
loia. is suspended in virtually the same man- 

ner as the small magnets in the Kelvin 
instrument. There is also on the same 
suspension system a mirror which turns 
with the coil. This instrument is " dead 
beat,^' that is, it moves to its maximum 
deflection without oscillating back and 
forth. The scale s is read by means of 
a small telescope t focused upon tha 
mirror 711, Fig. loia, the scale appear- 
ing to move past the hair mark on the 
mirror, the light from a lamp or window 
being thrown on the scale. This gal- 
vanometer is not, as a rule, as sensitive as the Kelvin galvanometer, but is not 
readily affected by external magnetism, which with its dead-beat quality renders 
it advantngeous where a portable instrument is required. The instrument is pro- 
vided with the usual shunts; the lead or shunt wires are connected at ir ir. 




20 



AMERICAN TELEGRAPHY. 



A'OLTMETERS, AMMETERS. 

Voltmeters and ammeters are now extensively used for measuring voltage and 
current strength respectively, and for line tests. These instruments have the ad- 
vantage that in measurements of E. M. f. and current strength the results are given 
upon a scale without further calculation. The instruments are also " dead beat/' 
and the portable kind require no leveling and are not materially, if at all, affected 
by external magnetism. In Fig. loi^ an ammeter is illustrated as it appears in 
practice. The voltmeter is practically similar in external appearance, Fig. loi^. In 
the type of instruments illustrated, a rectangular or oblate coil of ware pivoted on 



Fig. ioi^. 



Fig. iou 





jeweled bearings is placed in a strong magnetic field, also like the siphon recorder, 
which coil tends to turn when a current passes through it. The coil carries a light 
metal pointer, the outer end of which, when the coil turns, moves over the scale; 
the scale being calibrated to indicate, in the case of the voltmeter, the voltage 
at the terminals of the coil, and in the case of the ammeter, the strength of 
current, in amperes or milli-amperes, as the case may be, passing through the coil. 
The coil is moved by the current against the force of light springs, which springs 
return the coil to zero when the current is removed. Frequently the instruments 
are arranged for high and low readings in the one instrument. Thus Fig. loic 
represents a voltmeter which will indicate up to 150 volts on the upper scale and uj) 
to 15 volts on the lower scale. For the 15 or 150 volt scale, one lead wire is con- 
nected with the right-hand post, and the other lead with the post marked 15 or 150, 
respectively. There are usually two resistance spools in the base of the double read- 
ing instrument, one or the other of which is placed in series with the moving coil, de- 
pending on which scale is used in the test. The small push button at the right, when 
depressed, closes the circuit in the instrument during tests. In stationary instru- 
ments, such as are used in connection with storage batteries, the instruments are 
permanently in the circuit. The voltmeter and ammeter are alike in general con- 
struction, but in the case of the voltmeter the coil is of thin wire of high resistance, 
while the coil of the ammeter is of thick wire of very low resistance. The voltmeter 
consequently diverts but little current from the circuit being measured for voltage,, 
its resistance being very high compared to that circuit, and the ammeter consumes 
but little of the current, its resistance being very low relative to that circuit. The 
ammeter is placed in series in the circuit. The voltmeter is placed across the 
terminals of battery or instrument to be measured for e. m. f. or drop in voltage. 



TABLE OF TANGENTS 



12 



XABI^E OF XAXGEKXS. 



Dec. 

" 1 
1.5 

9 

2.0 

3 

3.5 

4 

4.5 

5.5 

6 

6.5 

7 

7.5 

8 

8.5 

9 
, 9.5 
10 
10.5 
11 
11.5 
12 
12.5 
13 
13.5 
14 
14.5 
15 
15.5 
16 
16.5 
17 
17.5 
18 
18.5 
19 
19.5 
20 
20 5 
21 
21.5 
22 
22.5 
23 
23.5 
24 
24.5 
25 
25.5 



; Tangent 


: Dec. 


: Tangent 


; deg. 


; Tangent: 


: i)i7" 


1 26 


i ^488" 


i 51 


L23 \ 


! .026 


i 26.5 


• .498 


! 51.5 


1.25 i 


: .035 


1 27 


.509 


i 52 


1.28 I 


: .043 


i 27.5 


.520 


! 52.5 


1.30 i 


i .0524 


1 28 


.532 


; 53 


1.33 1 


1 .061 


1 28.5 


.543 


: 53.5 


1.35 i 


i .070 


1 29 


.554 


i 54 


1 37 i 


I .078 


i 29.5 


.565 


i 54.5 


1.40 i 


i .087 


i 30 


.577 


I 55 


1.43 i 


i .096 


1 30.5 


.589 


i 55.5 


1.45 j 


i .105 


1 31 


.601 


1 56 


1.48 i 


i .113 


1 31.5 


.612 


i 56.5 


1.51 i 


1 .123 


: 32 


.625 


; 57 


1.54 i 


i .131 


325 


.637 


; 57.5 


1.56 ! 


i .140 


33 


.649 


i 58 


1.60 j 


i .149 


33.5 


.661 


i 58.5 


1.63 i 


1 .158 


34 


.674 


1 59 


1.66 1 


; .167 


34.5 


.687 


; 59.5 


1.69 i 


: .176 


35 


.700 


• 60 


1.73 i 


: .185 


35.5 


.713 


60.5 


1.76 i 


; .194 


36 


.728 


61 


1.80 i 


i .203 


36.5 


.740 


61.5 


1.84 ! 


1 .212 


37 


.753 


62 


1.88 i 


1 .221 


37.5 '' 


.767 


62.5 i 


1.92 i 


i .231 


38 . 


.781 


63 : 


1.96 1 


i .240 


38.5 i 


.795 


63.5 ! 


2. 1 


i .249 


39 1 


.810 


64 i 


2.05 1 


1 .258 


39.5 i 


.824 


64.5 i 


2.09 i 


i .268 


40 1 


.839 


65 ! 


2.14 I 


1 .277 


40.5 1 


.854 


65.5 : 


219 : 


i .287 


41 i 


.869 


66 \ 


2.24 j 


i .296 


41.5 \ 


.884 


66.5 ; 


2.29 ; 


i .306 


42 i 


.900 


67 I 


2.35 ; 


i .315 


42.5 \ 


.916 


67.5 i 


2.41 i 


: .325 , 


43 


.932 


68 : 


247 j 


.334 : 


43.5 i 


.949 


68.5 : 


2.53 i 


.344 i 


44 i 


.965 


69 1 


2.60 i 


.354 1 


44.5 \ 


.982 


69.5 ; 


2.67 \ 


.364 1 


45 i 


1.000 : 


70 : 


2.75 i 


.373 i 


45.5 i 


1.017 i 


70.5 i 


2.82 i 


.384 i 


46 1 


1.030 : 


71 : 


2.90 i 


.393 1 


46.5 i 


1.053 = 


71.5 i 


2.98 1 


.404 i 


47 i 


1.07 


72 i 


3,08 i 


.414 i 


47.5 i 


1.09 . 


72.5 ; 


3.17 i 


.424 1 


48 \ 


1.11 


73 \ 


3.27 i 


.434 ; 


48.5 ; 


1.13 


73.5 i 


3.37 i 


.445 i 


49 i 


1.15 


74 1 


3 49 \ 


.455 1 


49.5 i 


1.17 


74.5 ; 


3.60 j 


.466 i 


50 i 


1.19 


75 i 


3.73 i 


.477 \ 


50.5 i 


1 21 


75.5 : 


3.86 =• 



Deg. 


: Tangent 


"76 


4.01" 


76.5 


4.16 


77 


4 33 


77.5 


4.51 


78 


4.70 


78.5 


4.91 


79 


5.14 


79 5 


5.39 


80 


5.6T 


80.5 


5.97 


81 


6.31 


815 


6.69 


82 


7.11 


82.5 


7.60 


83 


8.14 


83.5 


8.77 


84 


9.51 


84.5 


10.38 


85 


11.43 


85.5 


12.70 


86 


14.30 


86.5 . 


16.35 


87 i 


19.08 


87.5 i 


22.90 


88 j 


28.63 


88.5 


38.18 


89 ! 


57.29 


89.5 i 


114.59 


90 ! 


Inf. 



CHAPTER VIII. 
ELECTRICAL TESTING. 

THE WHEATSTONE BRIDGE. MEASURING RESISTANCE; CAPACITY; ELECTROMOTIVE FORCE, 

ETC. LOCATING FAULTS ON TELEGRAPH WIRES, ETC. 



One of the most frequently used, as well as one of the most useful methods of 
testing, in telegraphy, is that known as the Wheatstone bridge method. The prin- 
ciple of the Wheatstone bridge has also been used in overland duplex telegraphy 
and is almost exclusively employed in submarine duplex telegraphy. 

The operation of the Wheatstone bridge is, it may be said, based primarily 
on the fact that, when the potentials at two points of a wire are equal, no flow of 
electricity will take place in the wire. 

In Chap. VI, it was stated that electric potential, or pressure, in a conductor de- 
creases, or falls, proportionately as it *' overcomes " resistance, etc. By the aid of a 




diagram similar to Fig. 102, the potential at any point of a circuit in which a current 
is flowing, (and of which the e. m. f. and resistance are known,) may be found, in the 
manner described in Chap. VI., and of which one or two additional illustrations may 
be given. It is assumed that the conductor is grounded at distant end. ■ 



THE WHEATSTONE BRIDGE, 



12 



Assume the resistance of the conductor represented by the horizontal line e to 
bei,6oo ohms and the e. m. f. by the vertical line p, 8o volts, as indicated. In the 
figure the vertical line p is divided into sections, each representing 5 volts; the hori- 
zontal line, R, into sections of 100 ohms each. By drawing a vertical line from any 
point of E until it intersects the line e and then by drawing, from that intersection, a 
horizontal line to p, the potential at that point of k will be indicated. Thus, in the 
figure the vertical, dotted line p' from 800 ohms on r, intersects, on e, the dotted 
line r, draw^n to the 40-volt section on p, thereby indicating tliat the potential has 
fallen through, or overcome, one half the resistance of the circuit. Similarly, at any 
other point of the conductor, the potential may be found. In an analogous 
manner, also, the difference of potentials between any two parts of a con- 
ductor may be found when the total e. m. f. and resistance of the conductor are known. 
Thus, it will be seen, by reference to the dotted lines, that there is a potential dif- 
ference of 20 volts between the 800 ohm section and the 1,200 ohm section of the con- 
ductor. 

That this difference of potentials exists could be proven if the terminals of a 
suitable measuring instrument, such as a voltmeter, were connected between those 
points, as outlined in the figure. The direction of the current which would flow in 




90 1900 MOO 



100 1000 900 8 30 700 600 500 «00 JOU ZOO 100 100 200 JOO 400 500 600 700 8 




T 




po 900 1000 1100 i?aa 1300 iaoo iSOO 



an instrument placed between those points, would be from the point of higher, name- 
ly, the 800-ohm section, to lower potential. If both terminals of the measuring in- 
strument were connected to, say, the 8oo-ohm section, it would be found that no current 
would flow in the instrument. This would be, of course, because, in that event, 
there would be no difference of potential at its terminals ; or, in other words, 
because the pressure at both terminals is equal. 

In Fig. 103 an illustration is given of a means of producing this equality of 
electrical pressure at the terminals of a conductor* In that figure there are two 
conductors, E, E,' represented, each of 1600 ohms, connected at one terminal with a 
common source of electromotiv e force of 80 volts. The conductors, for the sake of 

* Or an instrument, such ?s a galvanometer. ~~~ " ' 



124 



AMERICAN TELEGRAPHY. 



clearness, are shown as diverging to the right and left of the source of electromotive 
force ; the lines e, e', representing the slope of pressure along the conductors. 

It is plain from what has been said that at a point, say 800 ohms from p, along 
each conductor, e, r', the pressure will have fallen equally in each conductor, namely, 
to 40 volts. If then, the terminals of an instrument, such as a galvanometer g (or a 
relay) be placed, one at 800 of e, and the other at 800 of k' there will be no indica- 
tion of current electricity in the instrument, and, as a matter of fact, none will flow. 
If, however, one terminal of the galvanometer g' be placed at 800 e and the other at 
1200 e', its needle will be deflected, indicating the "passage" of a current 
through its coils, and the "flow," which will be from e to e', will be due to a potential 
difference of 20 volts, inasmuch as the potential at one terminal is 40 volts, and at 
the other terminal, 20 volts 



FIG. 104. 

















I 












P 




/ 


/ 


7_0 ^ 

40 _ 


"^ 


\^ 


» 




/ 












25 
25 
15 






-^ 




A 


1 J 




^\ 






iP 

1 


1 


1 1 1 1 1 1 i 1 


. t 1 1 r\ 


8 


00 700 600 


500 4 


00 


300 200 


100 




100 




400 400 ioo eao TOO S 


00 900 1000 


HOO 1200 1300 ^400 I5O0 IfiOO 


N 


f 










\ f 


{( ' 


T 




'' 



It is not necessary that the resistances of each conductor, or circuit, e, e' should be 
equal, in order that points of equal pressure maybe obtained. For example, since it is 
known that the pressure falls directly as resistance is overcome, if we have one 
circuit of 1600 ohms, and another of 800 ohms, connected with a common source of 
electromotive force, as in Fig. 104, it is evident the pressure will have fallen one- 
half at the point 800 ohms in the longer circuit E, and to one-half at the point 400 
ohms, in the shorter circuit e.' Hence, if we connect one .terminal of a galvanometer 
to E at 800, and the other terminal to e' at 400 ohms, there will be no flow of 
cmrent in its coils, the pressure at both terminals being equal and opposite. 

The strength of current flowing in each circuit would, it is true, be unequal ; 
for, by Ohm's law, in the case of e it would be .05 of an ampere, and in that of r' .1 
of an ampere. But the current strength does not enter into consideration here, ex- 
cept in so far as its heating effect upon the wire might vary the resistance. 



THE WHEATSTONE BRIDGE. 



12 



If then, we should arrange a combination of conductors, or circuits, of whicli 
we knew, and could vary at will, the resistance of one or more of the conductors, we could, 
by the use of suitable apparatus, ascertain the resistance of an unknown circuit by 
the introduction of resistance in the known circuit until we had brought about an 
equality of joressure at two given points, at one point on the known and one on the 
unknown resistance, which equality of pressure might be made evident ])y the failure 
of a suitable instrument to deflect its needle, or armature, when that equality 
has been reached. The principle aforesaid and a combination of circuits and appara- 
tus for the purpose stated, are availed of in the Wheatstone bridge. 

In Fig. 105, which is a theoretical diagram of the Wheatstone bridge, we have 
p, a battery exerting a pressure at a of, say, 80 volts. R u' are known resistances, 
consisting of coils of wire, each havijag a resistance of 800 ohms, b, is a resistance 
box, or rheostat, having adjustable coils, jc is a length of wire the resistance of which 
it is desired to ascertain, r and r', b and x, are termed " arms " of the bridge, and 
G is a galvanometer placed in a circuit, or wire, whose terminals are respectively con- 
nected as shown at t and t'. 



FIG. 105. 




It has been stated that as long as there is unequal pressure at the terminals of a 
conductor, current will flow in its coils from the point of higher to the point of 
lower potential, but that, when the pressure is equal, and opposite in direction, at 
those terminals, current will not flow. The resistance of the arms r' and r being 
equal in this case, if we adjust the known resistance b until no deflection of the gal- 
vanometer needle is perceptible, we may know that we ha\e rendered the pressure 
equal at its terminals t t'. When this result is accomplished the bridge is said to 
be balanced. 

Sup])osing that, to bring about this equality of pressure, it Avas necessary to in- 
sert 800 ohms in the rheostat b, it will follow that the unknown resistance .v must 
also be 800 ohms, and that such must be the case is evident from the fact that, in 
the case of the known resistance from a to z, via r, t and b, the pressure at t has 
fallen one-half, or to 40 volts ; , consequently, since equality has been produced at 
T J ', the potential at t' must also be 40 volts, which indicates that half of the total 
resistance from a to z via r' t, and x has been overcome and, since the flrst half, 
R.' is known to be 800 ohms, the second half, or .v, must be the same. 



126 



AMERICAN TELEGRAPHY. 



Ordinarily this conclusion is arrived at by considering that the arms of the 
bridge bear certain relations to each other when a *' balance" has been obtained 
in the bridge wire, and that relation is expressed by the " rule of three " formula : 
E ; k' : : B : ^. Knowing then the resistance of any three of the terms it is an 
easy matter to ascertain the fourth. For instance, in the case given we have 
(^) (k') (b) 
800 ; 800 : : 800 : x, which is equivalent to saying, x = ^ ^^^ 



800 



That 



IS. X 



640000 o 



As stated in the case of examples already given, it is not necessary that the re- 
sistances of the arms k k', Fig. 104, should always be equal — indeed, if that were the 
case the usefulness of the Wheatstone bridge would be much diminished— for by 
varying the resistances in e and e' it is possible to measure the resistance of an un- 
known wire very much greater than the combined resistance of all the coils of the 
rheostat b, or very much less than the resistance of its smallest coil. 

FIG. 106. 




For example. It is desired to measure the resistance of a wire, or any other 
substance, which we find to be greater than the total resistance of the rheostat. If, 
in Fig. 106, we place in e a resistance of 10 ohms, and in e' iooo ohms and find it 
necessary, in order to get a balance, to insert 10,000 ohms in b, it will follow that 
the unknown material x must have a resistance of 1,000,000 ohms for, since, atthe point 
T, we know the pressure has fallen through toVVo parts of the resistance from a to z, via 
E and b; at t' the pressure must have fallen through a proportional part of the 
entire resistance of the circuit from a to z, via e' and x^ which would be 

parts, and, therefore, also by rule of three: e : (e + b) :: e' : (e' + x), or 



1000+ X 
10 : looio 



IOOO : e' + ^ That is, 



lOOIO X IOOO 







1,001,000 r= e' + X. Then, 



as we know that the resistance of e' is 1000 ohms, x must equal 1,001,000—1,000 ohms, 
that is, 1,000,000 ohms. Or, we may obtain this result, as before, by the formul^j. : 

(e) (e') (b) ^ jQQQ ^ jQQQQ 
10 : 1,000 :: 10,000 : x; that is, x = = i,ooo,ooOo 



10 



THE WHEATSTONE BRIDGE. 



127 



Or the result may be obtained more easily yet by multiplying the known resist- 
ance of B by the ratio which r bears to r'. In this case the ratio is i to too, conse- 
quently, the resistance of x is 100 X io,ooo,or 1,000,000. 

In Fio's. 105 and 106, the terminals, a, b^ are shown as placed to earth. It will be 
apparent that since the earth acts precisely as if it were a conductor, having practi- 
cally no resistance, those terminals might be joined directly together in the Wheat- 
stone bridge without affecting in any way the results. 



FIG. 107. 




1000 ^100 10 10 lOOi^'lOOO 




If it is desired to measure a conductor, the resistance of which is less than the 
smallest coil of the rheostat b, it is only necessary to reverse the arrangement shown 
in Fig. 106 and place the 1,000 ohms in the arm R, and the 10 ohms in r'. If then a 
balance is obtained by the insertion of, say, 20 ohms, in b, the resistance of the con- 
ductor oc will be .2 ohms. For, as it is known that at t, the pressure has fallen 
through \%%% parts of the circuit from a to z via r b, so, at t,' the pressure must 

have fallen throuij^h — — parts of the circuit from a to z via r' 



Or, as 



(b) (e') 

1000: 10 



(B) 



10 X ^ 

Then^ 



200 



that is, .2 ohm. 



loX 20 

± lit; II ^' — — 

20 • ^- 1000 1000 

Or, in other words, the result may be obtained by dividing the resistance placed 
in B by the ratio which r now bears to r'; that is, 100 to i ; that is, 20 divided by 100 
equals .2. 

If greater or less resistances tlian those above chosen are required to be measured 
by the Wheatstone bridge method, it may be done by still further increasing the ratio 



128 



AMERICAN TELEGRAPHY. 



between the arms r r' of the bridge, if the capacity of the apparatus will permit. In 
some forms of the Wheatstone bridge the arms of the bridge are so arranged that a 
ratio of 10,000 to i is obtainable. 

Post office wheatstoxe bridge. — One form of the Wheatstone bridge as con- 
veniently arranged for actual testing is outlined in Fig. 107. It is commonly known 
as the "Post Office " pattern. The bridge is contained in a box represented in the 
figure by the dotted lines, r and r' represent the arms of the bridge, which are, re- 
spectively, made up of coils of 10, 100 and 1,000 ohms, as marked. Any of these coils 
may be employed, at will, by the insertion of metal plugs in the ordinary way. In 

FIG. 108. 




Fig. 107 the 1,000 ohm coils in r, r', are shown as in use, making the "ratio " of those 
arms equal, b is an adjustable rheostat, having resistance coils amounting in the ag- 
gregate to 11,110 ohms. K, k', are keys which, normally, keep the battery and gal- 
vanometer circuits open, but w^hen depressed close those circuits. G is a galvanometer. 
B a testing battery, x is the unknown resistance to be measured. 

The Post Office pattern of the Wheatstone bridge as used in practice is shown in 
Fig. J 08, with box, plugs, keys, etc. 




129 



130 AMERICAN TELEGRAPHY. 



Siemens wheatstone beidge. — Another form of the Wheatstone bridge, known 
as "Siemens " pattern, is outlined in Fig. 109. 

This form of bridge differs from the Post Office pattern chiefly in the arrange- 
ment of the coils of the adjustable rheostat ; the general connections are practically the 
same. In the Siemens arrangement the cpils are arranged in dial form as shown. 
The dial a, Fig. 109, is composed of 9 coils of 1,000 ohms each, so arranged that one 
plug inserted between the disc a and any one of the segments, (numbered from i to 9) 
will put into the circuit as many coils of 1,000 ohms each as may be marked on the seg- 
ment. Dial B consists of 9 coils of 100 ohms each, dial c of 9 coils of 10 ohms each, 
and dial d of 9 coils of i ohm each; respectively connected to the discs a\ a^^ a^ . 

It will be seen that the metal strip f' is connected to segment of dial a, and that 
the disc « of a is connected to segment of dial b; ^' of b to ^ of c; ^^ to o of d, and 
a^ of D to the strip h'. Apertures are provided between the disc and segments of the 
dials for the insertion of plugs, as shown. Assuming plugs to be inserted between the 
discs a and segments of all the dials, it may be seen that all of the coils of those dials 
are simply short-circuited. Also that the complete removal of a plug from between 
any one of the discs a and the segments o, 1,2, 3, etc., will open the circuit between f' 
h'. Or,if a plug be inserted between a and segment 6 of dial a, and another between a\ 
and 2 of dial b, and if the dials c and d be short-circuited by plugs between the discs 
and o, there will be in circuit, between f and h', 6,200 ohms, namely, 6,000 at a and 200 
at B. 

This arrangement of the coils of the rheostat simplifies considerably the act of 
changing the coils to get a balance, and also the summing up of the resistances in cir- 
cuit. 

This form of instrument is frequently provided with a separate set of keys 
mounted on a common base, as at k, Fig. 109, whereby the battery and galvanometer 
circuits are, respectively, closed and opened. 

The keys consist of three brass strips, having suitable contact points. The battery 
circuit is connected to the two upper strips; the galvanometer circuit to the lower strip 
and the lowest contact point. Strip 2 is insulated from 3 by a piece of hard rubber. 
The act of depressing the knob n, closes first the battery and next, the galvanometer 
circuit. When the finger is removed from the knob, the strips, of their own tension, 
rise, opening the circuits. This separate arrangement of keys has the advantage that 
they may be placed more conveniently for observing the deflection of the galvanome- 
ter than if permanently attached to the bridge box; it being understood that the resist- 
ance of the connecting wire of these keys may be neglected ; of course, it should not be 
excessive. 

In Fig. 109 the wire to be tested, x, is shown connected to the posts h, h'; the space, 
whose resistance is infinity, between the brass strips on which h and h' rest, being 
open. It is obvious that by opening the space between f, f', and closing that between 
H and h' the resistance x may be connected at r and f', instead of as shown, in which 
case the battery wire in the figure now attached to h' would require to be removed to f; 



MEASURING RESISTANCES, 



131 



MEASURING RESISTANCES BY SUBSTITUTION METHOD. 

By the aid of the tangent or detector galvanometer an unknown resistance 
may be measured by what is called the " substitution ", or direct deflection method. 

It is known that with a given electromotive force and resistance the current in 
the coils of the galvanometer will cause a certain deflection of the needle. 

When it is desired to measure, by the direct deflection method, an unknown 
resistance, .r, it is placed in circuit with a galvanometer g and a battery b. Fig. no. 
If the tangent galvanometer is used the de- pjq jjo 

flection is brought to a suitable point on 
the scale by changing the coils of the galvan- 
ometer and, if necessary, inserting more 
or less resistance in the galvanometer cir- 
cuit. The deflection is noted. The switct 
s is then turned to the right, which act cuts 
out the unknown resistance x and in- 
serts the rheostat r. r is adjusted until a 
deflection similar to that obtained with 
the unknown resistance is shown. The re- 
sistance thus inserted in r is equal to the 
unknown resistance. Of course this method 
is only available when the unknown 
resistance is within the range of the resistance of the rheostat. 




CAPACITY TESTS. 



It is frequently desirable to know the electro-static capacity of a wire or 
cable. This capacity may be ascertained by the aid of a standard condenser and 
certain other apparatus, shown theoretically in Fig. in, in the manner to be describ- 
ed. 

As has been stated, the capacity of the standard condenser used for this purpose 
is generally ^ or .| microfarad. In the figure k is an instrument termed a 
** discharge " key. It consists of a flexible metal strip r and rigid strips s s'; 
all supported on suitable frames. r is supported at p and is given a tension 
which, normally, holds it against s'. There are contact points on the surfaces of 
R, opposite s' and s. b is a battery of any required e. m. r. sc is a standard condenser 
with an assumed capacity of ^ microfarad, g is preferably a Thomson reflecting gal- 
vanometer. The first procedure is to obtain a constatit. This is done by depressing r 
against s, by which action it is seen that the condenser sc is charged by battery b, via 
wires i and 2. The strip R is held depressed for a stated time, say 30 seconds, 



132 



AMERICAN TELEGRAPHY. 



when it is quickly let go, thus peimitting it to break contact with s and make con- 
tact with s', thereby opening the battery circuit and allowing the condenser to dis- 
FTG. III. charge through the galvanometer g 

J} and wires 2 and 3. The extent 

^1 N of the "deviation," "throw," or 

" swing " of the needle, as indicated 
by the movement of the spot on 
the scale, is duly noted. The foregoing 
action may be repeated several times 
in order to verify the " reading. " 
If the capacity of the condenser 
or cable to be tested is known 
to be high, a low electromotive 
force, for instance, i volt, may 
be used in taking the constant. 
This, let us say, gives a 
deflection of 100 divisions on 
the scale. The assumed capacity of the standard condenser being \ m.f. we may then 
say the constant will be 200 divisions deflections for i microfarad with i volt e. m. 
F. The standard condenser is then replaced by the condenser or cable to be tested 
(as in Fig. 112). Assuming it to be an "armored" cable, the wires i and 3 are 
connected to the conductor and wire 2 to the armor. If the cable is not armored, wire 2 




CAPACITY TEST. 



S' 



P K 

It 




X 



CAPACITY TEST. 



is put to the earth direct. A preliminary test may be made to ascertain the approx- 
imate deflection due to the discharge of the cable. If the cable is a long one a " shunt" 
around the galvanometer will probably have to be used, even if but i volt be em- 
ployed in the test. The strip R is then depressed for, say, 30 seconds, charging the 
cable. The cable is then discharged and the deflection is noted. Assuming that it 
is necessary to use the \ shunt and that a deflection of 100 is obtained, it is plain 



MEASUREMENTS ELECTROMOTIVE FORCE. 1 33 

thatjWitliout the shimt,the deflection would be looo divisions. Hence, as the deflec- 
tion is proportionate to the strength of current and the current is proportionate to 
the potential to which the cable was raised, it follows that the capacity of the cable 
is ten times greater than that of the standard condenser, since, with the same e. m. 
F. it gives a discharge current ten times greater than the standard condenser. The 
total capacity, therefore, of the cable is 5 microfarads. The formula for this 

test is as follows : x = ^ where d is deflection due to standard condenser, 

d 

D the deflection due to unknown capacity of cable, k the capacity of standard 

condenser, and x the total capacity. Supposing the cable tested to be 20 miles in 

length the foregoing r3sult would show the cable to have a capacity of .25 microfarad 

per mile. 

MEASUEEMENTS ELECTEOMOTIVE FORCE. • 

The arrangement shown in Fig. 1 1 1 may also be used to measure the electro- 
motive force of a cell or battery. 

For this test a standard qqW. is used, that is, one, the electromotive force of which 
is known ; for instance, a carefully prepared gravity cell, the e. m. f. of which 
maybe taken as 1.079 voits. 

This test is made virtually as in the case of a capacity test, except that the " read- 
ing " is generally taken at the moment of charge, and it is based on the fact that the 
" charge ", or quantity of electricity which a condensor will accumulate, is propor- 
tional to the electromotive force of the charging battery. Thus, with the connections 
arranged as in Fig. iii, assuming that a deflection of loo divisions is obtained with a 
standard cell b; tlien if we substitute for b, another cell, calling it b', and get a de- 
flection of 200 divisions, the electromotive force of the second cell is evidently twice 
that of B. 

The formula for this test would be d : d':; b: x, where x is the e. m. f. of b'; 
Bjthe E. M. F. of cell b ; d,the deflection obtained with b ; d', the deflection obtained 
with b'. 

MEASURING INTERNAL RESISTANCE OF BATTERIES. 

The following is a simple method of measuring the internal resistance of a cell 
or battery. It is termed the " half deflection " method. The arrangement for this 
test may be similar to that shown in Fig. no. A tangent galvanometer is employed, 
the copper band of which is used. The cell or battery b to be tested is connected 
up with the galvanometer g and a rheostat r. The coils of the latter are at first short- 
circuited. 

We have seen that the currents in the tangent galvanometer coils are proportion- 
al to the tangents of the angles of deflection of its needle. Also that, according to 
Ohm's law, current strength in a circuit is inversely proportional to the resistance. In 
this test the electromotive force is furnished by the cell, or cells to be tested. The 
current flowing in the circuit consisting of the galvanometer band and the cell itself, 
is then equal to the quotient of thcE. m. f. divided by the resistance. This current 
deflocts the needle a certain distance. It is immaterial in this test what the exact 



134 AMERICAN TELEGRAPHY. 

Strength of the current may be ; that is, within the limits of the galvanometer. The 
deflection is noted. Assuming it to be 21.55^ of the scale, the tangent of the angle 
is .3889. It is understood that the resistance of the copper band is so little it may be 
neglected. The connecting wires should be so short or so thick that this statement 
may also apply to them. If now, by means of the rheostat, sufficient resistance is 
inserted in the circuit to bring the "pointer" to a place on the scale opposite 11.12°, 
we shall have, practically, halved the tangent of the angle of the first deflection, 
the tangent of 11.12° being .1944. Assuming that 2 olims were inserted to thus re- 
duce the deflection it is clear that the internal resistance of the battery is also 2 ohms. 
For, since we have halved the tangent of the angle of deflection, to which the cur- 
rent is proportional, and have not disturbed the electromotive force, it follows that 
we must have doubled the previously existing resistance of the circuit. 



TESTING THE CONDITION OF BATTERIES . 

The tangent galvanometer is also used to determine the condition of batteries, 
in the following manner : 

The deflection of the needle due to the current from one cell taken from the 
battery, and known to be in good order, is noted. This deflection will serve as a 
constant. The current from the entire battery is then passed through the copper 
band of the galvanometer. The deflection should be the same if the entire battery 
is in good condition, for, in that case, the current flowing through the galvanometer 
should be the same as when but one cell was used. {See Arrangement of Cells, etc.) 

In practice it is common to ascertain,by experiment with a given galvanometer, 
what the lowest deflection will be with a battery in good working condition, and, 
when the deflection falls below that point, to have the battery examined or renewed. 
If a newly set up battery should show an abnormally low deflection, or, in other 
words, an abnormally high resistance, the cause will doubtless be found in some one 
or two cells, which may be determined by testing the cells separately. 

It may be noted that the uniform deflections obtained under the different, but 
proportionate, conditions of electromotive force and resistance, when the battery is 
in good order, are due to the fact that the resistance of the galvanometer band used 
during, this test may, as already stated, be neglected. If a coil of high resistance 
were employed a different and not so simple a method of calculating the result 
would be necessary. 



LOCATING FAULTS ON TELEGRAPH WIRES. 

The " faults " that occur on telegraph lines are generally due to crosses, heavy 
escapes and grounds. The cross is caused by two or more wires coming together; 
the escape is caused by a partial contact of the wire with the ground, and the 
*' ground " is occasioned by the actual contact of the wire witli the earth. 



LOCATING FAULTS ON TELEGRAPH WIRES. 1 35 

On the occurrence of faults of the nature just mentioned, or analogous ones, the 
first step generally taken is to locate, or localize, the fault between two stations, or 
offices. This is done by the testing office asking some office located about the middle 
of tlie line to "cut " in on the defective wire. Call this office f. If the defect is a 
"break'' the station thus called in, will put on his "ground" wire. If this closes 
the circuit the break in the wire is evidently beyond f. f is then told to take off his 
ground and " cut " out, and a more distant office is called in on the wire. Should the 
"break'' be between the testing office and f, the putting on of the ground in f 
will have no effect, and that office reports the circuit open. In this case the testing 
office then calls up a nearer office and the same procedure is followed, until the trouble 
is located between two offices. 

To locate a " ground " between two offices, intermediate office f is asked to 
open the defective wire. If by so doing he opens the wire at the testing office the 
ground is beyond him, and a more distant office, g is called in. If the opening 
of f's key does not open the wire at the testing station the "ground " is between 
F and G and in that case the testing office then proceeds to call in a nearer office. 
This plan also applies to the locating of "escapes.'* 

In locating a "cross" between two or more wires the intermediate office is 
called in and requested to open one of the crossed wires. If, on his doing so, the 
testing office finds that wire now clear, the cross is beyond the intermediate office. If 
the cross still remains on the wire the trouble is evidently this side of the intermediate 
office, and a more remote office is next called in. 

In making the foregoing tests the chief operator uses the ordinary main line 
relay ; determining the extent of, or removal of the escapes, etc., by the pull of the 
retractile spring. 

Having located the trouble between two stations the testing chief operator then 
decides whether a test for a closer location of the fault is necessary. This depends 
sometimes upon the whereabouts of the linemen and the distance apart of the stations 
between which the fault has been located. Should it be deemed best to locate tlie 
fault more accurately, either of the electrical methods to be described may be utiliz- 
ed. In the case of a "dead" open fault, as it is termed, since it is most probable 
that at least one end of the wire is grounded, the nearest testing office beyond the 
break and on the side of the "ground" is requested to locate it by an electrical 
test. 

In ordinary practice, in this country, it is the custom to rely, almost entirely, 
on the " between office " test, especially when the line follows a railroad, in which 
case the lineman proceeds by train to the scene of the break and by keeping a 
close look- out can generally detect the trouble from the train. He may then, if fortu- 
nate enough, have the train stop to permit him to alight. If not it will be necessary 
for him to walk back, or to use a railroad velocipede from the next station. 

Where offices are widely apart on highway lines the question of electrical tests 
to locate faults as accurately as possible becomes more important, since the fault 
may be within a few feet or yards of one of the offices. But even in the case of 
highway lines electrical tests are not always resorted to ; the general rule being to 



136 AMERICAN TELEGRAPHY. 

send out linemen from each office with orders to ^^roceed until they meet; the first 
arriving at the fault to repair it if he can do so alone. 

When it becomes imperative to test for the exact locality of a '-break" in a 
wire, the only means of so doing is by a " capacity " test. {See Locating Faults by 
Capacity test.) 

Another source of trouble on telegraph wires is that due to a high resistance 
caused by poor joints, loose connections, etc. Such faults are best located by meas- 
uring the resistance of the wire from point to point by means of the Wheatstone 
bridge. 



LOCATING CROSSES ON OVERHEAD WIRES OR IN CABLES. 

When wires, whether overhead or in cables, are " crossed ", it is a compara- 
tively simple matter to locate the distance of the cross if the wires crossed are of 
the same resistance throughout, and, also, if there be no resistance at the scene of 
the cross itself. 

Locating a cross having no resistance — The procedure in that case is as 
follows : Suppose the wires a b, Fig. 114, each having a resistance of 10 ohms, per 
mile, to be crossed at the point x. The wires are first opened at z, and the loop 
formed by a and b via the cross is then measured from y, preferably by the 
Wheatstone bridge method. Assuming the resistance thus obtained to be 500 ohms, 
which will be the sum of the resistances of the two wires from y to x, it is an indi- 

FIG. 114. 

A A 

Y ^x: z 



cation that the cross is distant 250 ohms along either a or b, and as the wires meas- 
ure 10 ohms per mile, the fault is, evidently, 25 miles from the terminals at y. 

It is not, however, safe to take it for granted that there is no resistance at the 
point of contact, x, of the wires, and, therefore, a method in which the resistance, 
if any, at that point, may be measured and allowed for, must be employed. 

Locating crosses having resistance. — One such method is as follows : a and 
B, Fig. 114, are shown crossed at 2^, as before. If not already known, the total re- 
sistance of A is first measured. This is done by opening wire b at both ends and 
grounding a at z. Assuming this resistance of a to be 1,000 ohms. It is also sup- 
posed that B has a similar total resistance. Next open a at y, and b at z, and 
measure the resistance of the circuit thus formed, from y to z via x^ and call it 
1,100 ohms. It is then plain that the resistance of the *' cross" is the excess of 



ELECTRICAL TESTING. 



n7 



rBsistance over the normal resistance of either of the wires; that is, i,ioo minus i,ooo 
iiamely, loo ohms. 

The wires a and b are now measured as a loop, from y to Jt: and return. As- 
suming the resistance obtained to be Gob ohms, the resistance of the cross itself 



FIG. 115. 



jst te^t ^^^^ ''^''''' 



must now be deducted from that amount : namely, 100 from 600, leaving 500 ohms. 
The resistance of either of the wires from y to the cross is, therefore, 250 ohms, and 
this places the cross 25 miles from y. 

It has been assumed in the foregoing tests that the resistance of the two wires 
is practically the same throughout. When this is not the case a different plan of 
testing is followed ; namely, one in which the resistance of either of the wires is 
calculated from the measurements; or another in which, owing to the manner of the 
test, the resistance of but one of the wires is required. 

The first of these methods to be described is quite simple and will be under- 
stood by the aid of the diagrams accompanying the following description : First, 
measure the resistance of a with b open at both ends, as in Fig. 115, and call it, as 
before, 1,000 ohms. Next measure a and b, as a loopjfrom y to the cross x and return, 



FIG. 116. 



TOOokms 



J3 



^ Z 



through and including the resistance of the cross. Fig. 116. Assume it to be 700 
ohms. Next, open a at y, and b at z, as in Fig. 117, and measure a b from y to z, 
via x^ and call the result 1,100 ohms. This latter test also includes the resistance 
of the cross. If we now add the results of the Urst and second tests together, mak- 
ing 1,700 ohms, and subtract from that amount the result of the third test, that 
is, 1,100 from 1,700, it will be observed that we have Airtually cancelled the re- 
sistance of B from Y to ^, (Fig 116) including the resistance of the cross, and the 
resistance of a from x to z. This shows that the 600 ohms left after this can- 
cellation is the sum of the resistance of a from y to .v, taken twice, (Figs. 115 and 



138 



AMERICAN TELEGRAPHY. 



1 1 6.) Hence it is plain that the cross is at a point 300 ohms from y ; or, assuming 
the resistance of the wire a to be 10 ohms, per mile, the fault is 30 miles from y. 



FIG. 117. 
3^*^ test. TT60 oTuns 



T r^ 



It is thus seen that the actual resistance, per mile, of the wire b is not required to 
be known. 

The formula for this test would be 

A + L F 

X = 

2 

where x is distance of fault in ohms, a the result of ist test, l the result of 2nd test, 
and F the result of 3rd test. 

LOCATIN'G A CROSS HAVING KESISTANCE — A WHEATSTOXE BRIDGE METHOD. — Another 

method in which the resistance of one of the wires may be neglected is shown in 
Fig. 118, as usually outlined in the text books. In this figure x is the cross 



FIG. 118. 




^ z 



as before, the test being made from station y. a and b are the crossed wires. 
G is a galvanometer, one terminal of which is attached to line wire a at 
station y ; the other terminal to point k, also in station y. r is a known, moder- 
ately low resistance, inserted between the line wire b at r, and the point k. r is an 
adjustable resistance, inserted between k and the ground, b is a testing battery 
attached to b at c, as shown. The distant end of wire a in z office is insulated ; that 
of B is grounded. 



lOCATING FAULTS. 



539 



At first siglit tlie foregoing diagram may not be recognized as an arrangement 
of the Wheatstone bridge, but it is so, nevertheless, as will perhaps be more 
clearly seen by reference to Fig. 119, in which the arrangement of wires and ap- 
paratus is modified to conform more closely to' the conventional Wheatstone bridge. 
B, between c and the cross x, forms one arm of the bridge ; r, the known resistance, 
forms the other ; a, between the galvanometer and the cross, forms the chief portion 
of the bridge wire, and b, beyond x, is balanced by the adjustable resistance k. 

Since the wire a is in the bridge wire on one side of the cross and 
open on the other side of the cross it is easily understood that its 
resistance may be neglected, and since wire b is not tested through the cross 
the resistance of the cross may also be overlooked. Having made the ar- 
rangements as shown, a balance is obtained in the usual way, by adjusting r until 
equilibrium is established in the galvanometer. 



FIG. 119. 




For example. Let us call the portion of the wire b, between c and .r, f, and 
that portion between ^and the earth at z, r'. When a balance is secured in the 
Wheatstone bridge it is known that ris to r -fR,as f is to f -|- f'. Assume that the 
resistance of r is 20 ohms, and that it is necessary to insert 480 ohms in k to obtain a 
balance. We have, it is also assumed, previously ascertained that the total resist- 
ance of wire B, from Y to z is 1,000 ohms; that is, f + f' = 1,000 ohms. As the 
total resistance of r -f r is 500 ohms, it is self evident that r is -^-^ of that total 
resistance ; that is, ris 4e^^ S^^- Then, as f is to f -h F',as r is to r + r, f will 



I40 



AMERICAN TELEGRAPHY. 



be 2V o^ T,ooo; in other words, 40; which is obvious from the fact that 20 is to 40 as 
480 is to 960, which is the equivalent of saying that the arm r, of the bridge, is to 
P as the arm r is to f'. 

The usual formula for this test is : 



F = B X 



R + r 
where F is distance of fault in ohms ; b is total resistance of wir.e b; and r and R are, 
respectively, resistances of bridge arms. 



LOCATIXG FAULTS BY VAELEY LOOP TEST. 



To locate a " ground " on a wire or cable would be comparatively easy if it were 
known that the ground itself had no resistance, for in that case it would only be 
necessary to m.easure the resistance of the wire from the testing end to the ground, 
and then, (as in locating a " cross" under similar conditions) divide the result by the 
known resistance of the wire, per mile. But, as in the case of "crosses " also, there 
is generally more or less resistance at the point of contact with the earth, and as the 
amount of this resistance is not known, some method of locating the "fault" must 
be employed in which the unknown resistance may be neglected. 

The Varley loop method, the connections of which are shown in Figs. 120 and 

121, is one such method of locating 
a ground. It will be seen that it 
utilizes the TTheatstone bridge. In 
making this test it is necessary to 
have two parallel wires, one of 
which is the defective wire. These 
two wires are first connected as in 
/Fig. 120, forming a loop, the resist- 
ance of which loop is measured by 
the bridge method ; the presence of 
the ground, or fault f, not interfer- 
ing with this measurement. It is as- 
sumed that the wires of the loop are 
of practically equal resistance per 
unit of length, throughout. 

The " detector " galvanometer may be used for this test. It is placed in the 
"brid2:e " wire of the Wheatstone bridw. 

The connections are next made as in Fig. 121 in which a b are arms of the 
bridge ; w is the *' good ' ' wire of the loop, and w' is the defective wire, connected, 
respectively, to the bridge box terminals at b and x\ w' being indicated by the 
curved line ; the fault by f. The battery is connected as shown, one pole being 
p]aced to ground. r is the usual adjustable resistance of the bridge. 




VARLEY LOOP TEST. 



VARLEY LOOP TEST. 



141 



When these connections have been made the keys are depressed and resistance 
is inserted in R until a balance is secured. When this balance has been secured 
it may be seen by reference to Fig. 122, that the fault is moved, as it were, to the 
middle of the loop now formed by the wires w w', and the resistance r, just added to 

w' to bring about the balance. 
FIG. 121. The distance of the fault f, from 

Xy in ohms, is then found by the 




use 



of the formula, f = 



where f is the resistance of w', be- 
teen ./^ and f; l the known resistance. 
Or, it may be found by the formula, 

F = w' — • ~- ; w' beino- the resistance 
2 * 

of ihe defective wire; these formu- 
lae being the equivalent of each 
other. That such is the case will be 
obvious on considering that w' is one 
half of L. 
These formulae may be reasoned out, aided by Fig. 122, as follows : Assum- 
ing that the resistance of the loop as first measured is 30 ohms, the resistance of 
each wire will be 15 ohms. Assume also that it was necessary to insert 12 ohms 
in R to secure the balance. We may see, Fig. 122, that in procuring the balance a 
certain portion of w' has been added to w, namely, that portion of w' between the 

FIG. 122. 



VARLEY LOOP TEST* 




fault f and the junction j of w with w'. Therefore, it is plain that as much as has 
been added to w has been subtracted from w'. Hence, in obtaining a balance it 
must have been necessary to insert in r a resistance equal to the sum of that 
which has been added to w and subtracted from w'. In otlier words, the resistance r 
added to w' to procure a balance against the total resistance of av plus that taken 
from w', is equal to twice the resistance of that portion of w' between f and j. Hence, 
the resistance of w' between f and j must be one-half of 12, the added resistance, 
namely, 6 ohms. That being so, it must follow that the resistance of the portion of 
^y', ii'omx to f, will be equal to the total resistance of w' (namely, 15 ohms) nnnus the 



142 AMERICAN TELEGRAPHY. 

resistance of w' from f to J, that is, 15 — 6, 01-9 ohms. From which we may see that 

the formula f = w' , or f = ic , is correct. 

2 ^2 

The resistance, per mile, or per foot, of the wire being known, it is then a simple 
matter to calculate the distance of the fault from the testing station. In the forego- 
ing it has been assumed that the arms a, b, of the bridge have been equal. When such is 
not the case, the actual resistance of r should be calculated in the usual way before pro- 
ceeding with the formula. In making this test, the faulty wire must always be con- 
nected to the bridge box at x. Figs. 121, 122, in order to get a balance, except when it 
happens that the resistance of the "good " wire used to form a loop with the defective wire 
is so much less than the latter that the resistance of the indefective wire, added to that of 
the portion between x and f of the defective wire, is less than the resistance from the 
testing station to the fault, of the defective wire, in which case the position of wires, w 
and w' must be reversed ; the wire of low resistance being connected to e at x, and the 
faulty wire w', to arm b at /^. The two wires are then measured as a loop as before. 
The battery is then "grounded," and a balance obtained by the insertion of resist- 
ance in R, also as before. But in this case the result of the second measurement is 
added to that of the first and their sum is divided by 2, which gives the distance in 
ohms from ^ at b, to the fault on the defective wire. 

The formula for this latter test is f= , where l is the loop and r the added 

2 

resistance. 

The foregoing method of testing is commonly known in the larger telegraph offices 
of this country as the " pig tail " test; perhaps due to the resemblance, in some dia- 
grams, of the " fault " to a queue.^ 

In making these and similar tests, the probable existence of defective joints in the 
circuits should be taken into consideration, as such joints would, of course, impair the 
accuracy of the results, and possibly render them useless. 

Regular electrical tests of circuits will, however, disclose in advance any abnormal 
resistance that may develop. 

LOCATING FAULTS BY CAPACITY TESTS. 

Breaks in wires are sometimes located by aid of the " capacity" test. 

When the capacity, per mile, of the wire, or cable, is known, its total capacity, 
up to the break, is measured in the manner described {see Capacity tests) and from 
this the length of the conductor up to the break n is calculated. For example, assum- 
ing the capacity of a conductor to be .25 microfarad, per mile, and that the measured 
fragment of the conductor has a total capacity of 5 microfarads, the break is evidently 
20 miles removed from the testing point; that is .23^= 20. 

When the capacity, per mile, of the cable is not known in advance, the capacity of 
a similar conductor, or cable, whose length is known, is measured, and the capacity,, 
per mile, or per foot if need be, thus ascertained. 

This capacity, per mile, or, per foot, is the more readily learned when the break 
has occurred in a cable composed of two or more conductors. 

In this measurement a complete *' break" is assnrned. 

* To test for a swinging cross the method known as the Diehl arrangement may be used. Tai^:e one of the swinging: 
wires, and connect it at a point beyond the cross with a good wire, thus forming a loop, the resistance of which is meas- 
ured.' The second swinging wire is left open at the distant point, but is grounded at the testing station; a relay and a 
strong battery being placed in its circuit. The bridge is then balanced, as in Fig. 121, so that the galvanometer is not 
affected when the swing comes on. The relay in the second crossed wire will, however, click at each contact of the swing- 
ing wires, showing that the balance is obtained. The locality of the cross is then ascertained by the formulae given for tlie 
Varley loop test. 



INSULATION RESISTANCE, ETC. 1 43 



INSULATION RESISTANCE OF WIRES AND CABLES.— MEASURING, ETC. 

As already mentioned, those substances wliicli possess very inferior electrical 
conducting qualities, are termed " insulators," and the material of the substances is 
spoken of as insulating material. 

In order to insure the passage of a current throughout the length of a conductor, 
it is essential that no other conductor shall come in contact therewith. For example, 
if a " bare" telegraph wire should be allowed to come in contact with the earth at a 
number of places, it would be practically as useless to attempt to convey signals from 
one end of the wire to the other, as it would be to convey water from one end of a 
pipe to the other if the sides of the pipe were perforated with large holes at diflferent 
points of its length, inasmuch as under the conditions stated the electricity would 
" escape ' ' from the wire, virtually as would the water from the pipe. 

In the case of the " escape " of the electric current under those conditions, the ex- 
planation is simple, namely: at the points where the bare wire touches the earth the 
potential falls to "zero " and, thus, as, normally, the electrical condition of the wire is 
zero, it is evident that such portions of the circuit as are beyond the point of earth 
contact can not be subjected to any difference of potential. For example, assuming a 
telegraph wire extending from a to b, with an electromotive force at a. If the wire be 
connected direct to earth at an intermediate point, ^, the potential at that point falls 
to zero ; hence, the remaining portion of the wire between x and b will remain at zero 
and, consequently, no current will flow between those points. 

Hence, in the employment of aerial telegraph lines, the wires are strung on poles, 
and at each pole the wire is supported by a '* glass " insulator, that the " current " may 
not " escape " to the earth via the wood of the pole ; glass being a better insulating ma- 
terial than wood, more especially when the latter is damp. As air is one of the best 
known insulators the bare wire may be freely suspended in it without any danger of 
the current escaping to earth. 

When wires are to be laid underground or underwater, it is necessary, for the same 
reasons, to cover them with some form of insulating material, as, for instance, gutta- 
percha, India-rubber, etc. As the working condition of telegraph wires, and, in fact, 
all electrical conductors, depends very largely upon the excellence of the " insulation " 
of those wires, it becomes very desirable to maintain the insulation practically intact, 
and in all large telegraph oflices, regular tests are, as a rule, made to ascertain the con- 
dition of the insulation of the circuits. This is termed measuring the resistance of the 
insulation, or, for brevity, the "insulation resistance," of the circuits. 

*rhe total insulation resistance of an overhead wire depends mainly upon the 
" joint " resistance of all of the " resistances " at the various points of " escape " ; for in- 
stance, at the insulators; at points where foliage touches the wire, etc. In the case of 
cables the total insulation resistance may be said to depend upon the joint resistance 
of the various resistances of each portion of the insulating material. For instance, 
there being 5,280 feet in one mile, if one foot of the insulating material of a cable has 
an insulation resistance of one million ohms, the total insulation resistance of one mile 
of such a cable would obviously be the joint resistance of 5,280 circuits in multiple, each 



144 



AMERICAN TELEGRAPHY. 



having a resistance of one million ohms. This subject is alluded to further in connec- 
tion with the measuring of the partial insulation resistance of telegraph wires. 

For measuring the insulation resistance of overhead telegraph wires or aerial 
•cables when the " insulation " is not very high, a moderately sensitive galvanometer, 
«uch as the "detector," maybe used, in connection with a Wheatstone bridge; the 
** detector " being placed in the bridge wire and the arms of the bridge suitably pro- 
portioned, as explained in chapter on the Wheatstone bridge. But, in general, for 
insulation tests the " direct" or " substitution " method is adopted, that is, the unknown 
resistance is compared with a known resistance and the resistance of the former is cal- 
culated from the results thus obtained, and a Thomson reflecting galvanometer or a 
sensitive tangent galvanometer is employed: In what follows the employment of the 
former is assumed. 

Ordinarily, the cofistaiit for this test may be said to be the resistance necessary to 
l)e introduced into the galvanometer circuit, which, with i volt e.m.f., will give i di- 
vision deflection on the scale. But, in practice, what may be termed a working con- 
stant is used. This working constant is obtained as follows: 

Referring to Figs. 123, 124, a reflecting galvanometer g, and a shunt s, are placed 
in circuit with a battery B, of, say, 100 volts, and a known resistance R, say, of 100,000 
ohms. The -g-Jg- shunt is generallv 

necessary. When this shunt is em- fig. 123. 

ployed, the multiplier \s> 1000. {See 
Shunts). 

If the deflection obtained with 
this known resistance, electromotive 
force and shunt be, say, 250 divi- 
sions, it is plain that, without the 
«hunt, the deflection would be 
250,000 divisions. Therefore, since 
the deflections of the reflecting 

galvanometer are practically proportional to the current, and the current is inversely 
proportional to the resistance, it is clear that, to reduce the strength of curent to such 
an extent that it would deflect the needle but i division, it would be necessary to in- 
troduce into the circuit 250,000 times 100,000 ohms. For, by simple proportion i: 
250,000:: 100,000: x^ namely, 25,000,000,000 ohms — or 25,000 megohms; a megohm 
standing for one million ohms; consequently the " working constant" would be, with 
100 volts, 25,000 megohms for i division deflection. 

Having obtained this constant it is apparent that any resistance less than 250 
megohms may be measured by this apparatus, and the unknown resistance will be 
equal to the quotient of the constant divided by the number of divisions obtained with 
the unknown resi stance in circuit. For example, if an unknown resistance be substi- 
tuted for E, Fig. 123, and a deflection of 50 divisions be obtained, without the shunt, 
the resistance woul be ^^'""Vo^ "'°°" — 500,000,000 ohms. Or, this conclusion may be 
reached in another way. For example, assuming, as before, that, with 100,000 ohms 
in the galvanometer circuit, we get, by calculation, 250,000 divisions, without the shunt, 
and an unknown resistance ^ives 50 divisions, (without shunts) it is evident that the 




INSULATION RESISTANCE, ETC. 145 

unknown resistance is 5,000 times greater than 100,000 ohms, since it must have re- 
duced the current 5,000 times, (as evidenced by the diminished deflection). Hence the 
known resistance, 100,000 X 5,000 = 500,000,000 obms, as before. 

The usual connections for this test are outlined in Fig. 1 24, in which g is the gal- 
Tanometer; i k is a reversing key; c is a cable, or line wire (the unknown resistance); 
R is the known resistance, b is the battery and s k, a key for short-circuiting the gal- 
vanometer, sw, is a switch by means of which the cable or other conductor, and the 



FIG. 124. 



I 



c 




lo WMV\i — \ 

i ^ 



known resistance, may be alternately placed in circuit with the galvanometer, as 
desired. If it is a cable that is undergoing test the cojiducior of the cable is connected 
to the switch, as in the fignre. ^. v 

The reversing key has several functions, namely, to place the batte.y t#|th€r:.cable^ 
to reverse the jioles of the battery, according as one or other of its keys is depressed, 
and to " discharge " the wire or cable when both keys are up. > 

In making this test care must betaken to " short-circuit " the galvanometer before 
and for a few moments after the battery is placed to the cable and when the cable is 
discharged; otherwise the needle may be injured. Care should also be taken to con- 
nect the galvanometer between the battery and the cable, as by so doing any slight es- 
-cape in the battery may be neglected. 

If it is desired, and it is sometimes necessary, to begin by taking the regular con- 
stant for this test, (tliat is, the resistance necessary to introduce into the circuit, 
which with i volt will give i division deflection,) it may, of course, readily be taken, by 
placing I volt in circuit with the galvanometer and the known resistance, and noting the 
deflection. Having obtained this constant, a working constant is then found by mul- 
tiplying the constant obtained witli i volt, by the number of volts to be used in the 
test. Thus, if with i volt the constant is i division with rz, 500, 000 ohms in circuit, and 
it should be intended to make tlie tests witli a battery of 100 volts, the working con- 
stant would be 1 division with 250,000,000 ohms in circuit. An advantage in usingthe 
full battery in taking a constant is that in case any of the battery cells are faulty the 
results will not be affected inasmuch as the fault will have affected the constant as well 
as the actual test and to a relatively similar extent. 

In place of the resistance box r, containing the coils of resistance used to obtain a 



46 



AMERICAN TELEGRAPHY. 



constant^ a plate of carbonized material set in glass, and measuring one million ohms 
from binding post to binding post, {SeeY\^. 125), is frequently employed. It is gen- 
erally known as the " English " megohm 
PIG. 125. plate. 

It is preferable to use large resistances 
when the unknown resistance is large ; and 
also to employ for the actual test a battery 
of high electromotive foree. In making 
this test the resistance of the galvano- 
meter, like that of the copper band of the 
galvanometer in other tests, may be neglect- 
ed, it being so low, relative to the total 
resistance of the circuit. 




PAETIAL INSULATION RESISTANCE OF TELE- 
GRAPH LINES. 

It is quite frequently desirable to know 
the insulation resistance of a section of a 
circuit which is not directly accessible. 

For example, Fig. 126, assuming a wire 
tested at a to have an insulation resistance 
of 600,000 ohms from A to c, and tested 
from A to B, to have an insulation resis- 
tance of 1,800,000 ohms, and that it is des- 
ired to know the insulation resistance of 
the wire between B and c. 
It may fairly be assumed, for the purpose of the test in question, that the sections 
of the wire a to b and b to c, are in multiple, as regards the testing office, and in so 
far as the insulation resistance of the two sections is concerned. 



MEGOHM PLATE. 



FIG. 126. 






O 



-^ 



1. 






To illustrate: In Fig. 126, w w, is the wire; open ^t c; grounded at a; 
cut through at b. r may represent the joint insulation resistance of the 
" escapes " between a and B,and r the joint resistance of all escapes from b to c. 

Assume the distance from a to b to be 20 miles; b to c, 30 miles. Then 



TESTING INSULATORS. 



147 



A to c will be 50 miles. The resistance of the wire itself may be placed at 250 

ohms. It is then very evident that 250 in a total of 600,000 ohms may be easily 

neglected. Therefore, in making the test, the two sections, as represented by R and r, 

may be treated as though the terminal of each emanated directly from 

A, as shown in Fig. 127. 

^^^* ^^7- If then we test section r, with the 

wire open at b, and find, as stated, 

an insulation resistance of 1,800,000 

ohms and, then, with the wire cut 

through at b and open at c, we find 

a total insulation resistance of 600,- 

000 ohms, we know that the latter 

must be the joint resistance of both 

sections, namely, R, ?. 

Having, then, this data, and knowing the formula for obtaining the joint resist- 

rX r 
ance x, of two circuits, R and r, namely, x =-—--' (see Chapter III.) it is plain that 

R-t-i 

we may state the resistance cf the section fiom b to c, calling it r, (and, for the pres- 
ent, we may omit the ciphers) as follows; — 




i8Xr 



i8+r=^ 
It only remains to calculate from this the value of r. 

We can now clear the above equation of fractions if we multiply the right hand 
term, that is 6, by the divisor of the left hand term, and then we shall have, without 
having altered the value of the equation, 



Xr=io8+6 r 
r =108+ 6 r 



Again, if we subtract 6 r from the right hand term of the equation, and 6 r, from 
the left hand term, we shall get, without yet altering the value of the equation, 

12 r = 108. Consequently, if 12 r =108; i r will equal = 9, and, therefore, we 

12 

find that the insulation resistance of the section between b and c is (adding ciphers 
again) 900,000 ohms. 

To prove this it may be asked, what would be the joint resistance of the two sec- 
tions, one having a resistance of 1,800,000 olims, the other, 900,000 ohms. 

^-, . ■ 1,800,000X900000 

Obviously, X——- -^ = 600,000 ohms. 

1,800,0004-900,000 

The formula for ascertaining the insulation resistance of the distant section is then 
as follows: r = . x J, where r is the near section and j is the joint resistance of 

R — J 

k and r. 

But there is a simpler means than the foregoing of obtaining this information, if 



148 AMERICAN TELEGRAPHY. 

the " direct '' deflection method of measuring insuhition resistance he employed, [see 
page 144.) 

Assuming that a Tliomson reflecting galvanometer haying a T^'orking constant of, 
say, 36.000,000 ohms is used. 

If the section from a to b gives, without a sliunt, a deflection of 20 divisions, the 
insulation resistance is evidently ^^-^y^ ono _ 1,800,000 ohms. If the sections a to b 
and B to c, that is v. and r, tested together, give a deflection of 60, their joint resist- 
ance must be -2-S^|g-S-2-2- =600,000 ohms. Sincere know that 20 divisions of the 60 
thus obtained are due to e, the balance, 40 divisions, will be due to ;-. and, therefore 
section b to c, that is, ;- will be 36'"^g- ooo = 900,000 ohms. 

If a tangent galvanometer be used, it is only necessary to deduct the tangent of 
the angle of the deflection obtained by the first section from that of the tangent ob- 
tained by the joint resistance of both sections, in order to get the deflection due to the 
distant section, which latter, divided into the constant of the galvanometer, will give a 
quotient equal to the insulation resistance of the circuit. 

The foregoing method of ascertaining the insulation resistance of remote sections 
is not limited to two sections, as will be readily seen, on consideration. 

The average insulation resistance of the respective sections, per mile, may be as- 
certained by multiplying the total insulation resistance of the section by the number 
of miles in each section. Thus, the insulation resistance, per mile, of the section a to b 
will be 1,800,000 X 20 = 39,000,000. That of section Bto c, will be, 900,000 X 30 = 
27,000,000 ohms per mile; it having been ansumed that those sectioi]S were 20 and 30 
miles, in length, respectively. 

Further remarks on electrical testing will be found in connection with the electri- 
cal tests of wire and insulated cables at the factory. (Pages 509 to 531.) 

The voltmeter may be used to measure voltage between different parts of a cir- 
cuit, and, in combination with the ammeter, to measure resistance. Thus the resist- 
ance of an instrument k may be measured by placing an ammeter in series with it 
and a voltmeter across its terminals. If in such a case a reading of .5 amjieres is 
obtained, and 20 volts drop across the terminals of R, by Ohm's law {see page 6) the 
resistance of R is --f- = 40 ohms. If. on the other hand, the resistance of. R is already 
known, the carrent isctdculated by Ohm's law |ij- =: | = .5. 

To measure resistance or insulation resistance by the voitmeter, first measure 
the E. M. F. of testing battery, using that scale which is nearer the E. M. F. of bat- 
tery. Then place the voltmeter in series with the Ijattery and line or instrument to 
be tested, exactly as a galvanometer would be placed, and note the deflection in volts. 
It will of course be less than in the first case. The unknown resistance R will be 
found by the following formula. 

II = r X (v — v') -f- T\ 
where r is the resistance o£ the voltmeter coil, v is the E. M. F. of battery, and 
v' is the second deflection in volts. The resistance of the voltmeter coil is usually 
marked on the instrument. When using the voltmeter to measure high resistance, 
the voltmeter is connected like g in Fig. 123; when used to mea-ure the insulation 
resistance of a line or cable, it is connected like G, Fig. 124, omitting the shunts 
and reversing key. The voltmeter may also be usedinj^lace of G, Fig. no, in measur- 
ing resistance by substitution method. {See page 120.) 



TESTING INSULATORS. 



149 



MEASURING i:S^SULATION KESISTANCE OF INSULATORS. 

Since tlie total or " absolute " resistance of the insulation of an overhead wira 
depends upon the joint resistance of all the points of escape throughout its length, the 
insulation resistance of the " insulators" used on the poles to support the wires be- 
comes an important factor in the maintenance of the " insulation " of the circuit as 
a whole. 

The material of the insulators used in this country for telegraph and telephone 
overhead wires is almost exclusively glass , made in the well-known bell form. 

The electrical resistance of glass varies very materially with the quality of the- 
material, and specifications for insulators frequently stipulate that each insulator shall 
have a certain electrical resistance. The test to determine this resistance may be 
made practically as follows: 

A trough T, Fig. 128, is provided, in which metal supports /, resembling invert- 
ed tumblers, are placed. Into these supports the insulators x, to be tested, are in- 
serted, upside down, as shown. The trough, the supports and the insulators are nearljr 
filled with acidulated water, care being observed that the water does not get over, 
or upon, the edges of the inverted insulators. 

Bent Aviresare then plunged into 
each of the insulators in the man- 
ner indicated and these are then 
connected with the galvanometer 
G. Another wire which includes 
a battery, n, is led into the trough 
to complete the circuit. This 
wire may be attached to a copper ^^ 
plate, as e. A reversingkey may be u ^^ 
employed as in other insulation j 



FIG. 128. 




II 



tests. The constant of the 
galvanometer is taken as usual in the 

direct deflection method test. Assuming, as shown in figure, that 

four insulators are to be tested the result obtained in this case will be the joint resis- 
tance of the four insulators. The result should be multiplied by 4, and if the product 
is above the specified requirements, the test is satisfactory. If below, each in- 
sulator should then be tested separately until the cause of the low insulation is as- 
certained. Of course, in practice, the test is not limited to four insulators at one time. 
Another arrangement for the same purpose is shown in Fig. 129. In this the- 

insulators are suspended in the water in 
^.r^^-^rrrr^^yr,^^^^^ trough T by means of a cover r. One ter- 

■^^ ^ ^^^ ^^^^^'^^ ^'' ^^ ^^^^ ^^^'^ ^'' terminates in the- 
trough; the other end e, is held in the 
hand and is dipped into one insulator after 
another, tlius completing the circuit tlirouo-ji 
each. When the deflection of tlie ir.il- 
vanometer needle does not exceed anes- 
tiblished ])oint, the insulators are accepted, 
otherwise lliey are rejected. 



FIG. 129. 




CHAPTER IX. 

THE DELANY LINE ADJUSTMENT. 

During the prevalence of rainy weather much delay is frequently occasioned on 
poorly insulated wires and even on comparatively well insulated wires, by lack of 
proper adjustment on the part of operators at some of the "way " stations. 

The cause of this is, generally, that the partial grounds formed by numerous "es- 
capes'' have sufficed to establish a current between the battery and a point be- 
yond the unadjusted relay, which current Hows, notwithstanding that a key at some 
point beyond may be open. 

For example, in Fig. 130, a telegraph line is shown with batteries b b,' at the 
terminals x, y; a relay, R2, at an intermediate station, and relays r^ Kg, at x and y. 
Escapes e, e, e, due to defective insulation, are indicated as between E2 ^^^ the 
battery b, at x. 



FIG. 130, 




Assume those escapes to amount in the aggregate to a partial " ground ", and 
thatjWhen key k is closed, the major portion of the current from b will pass, by 
way of those escapes, to the earth, and only a small portion will assist battery b', at 
Y, in operating relay Rg. 

Then, if the operator at the intermediate office Rg ^^^ arranged his adjustment 
for the current due to b' at Y, it is plain that, as far as relay Ro is concerned, it mat- 
ters little whether key k, at x, be open or closed, inasmuch as only a trifling 
change in the strength of the current passing through R^ will be effected by such 
action of key k. For, whether key k be open or closed, the current from y will con- 
tinue to flow as long as the partial ground is maintained at e, e, e. If, however, it 
were possible for the operator at x, by some means, when he opens his own key, to 
open the line at y also, thereby cutting off the battery b', the line would be cleared 
of all current for the moment, and the relay, Rg, would respond. 



DELANY LINE ADJUSTMENT. 



I SI 



This result is ingeniously accomplished by the Delany *' line adjustment," or more 
correctly, perhaps, "escape" nuUifier, in the manner illustrated in Fig. 131. 

In this figure r' is a Morse relay at x, Rg is a relay at a, and Rg a relay at y. 
This may Le supposed to represent a railroad " way " telegraph line, with one 
station between the dispatchers' offices at x and y. 



FIG. 131. 




DELANY ESCAPE " NULLIFIER "(THEORY). 



The apparatus used to open the circuit simultaneously at both ends of the line is 
ehown to the left of relay r' at x, and to the right of R3 at y. 

It consists of an *' extra " electro- magnet em, in addition to the usual sounder 
s, placed in the local circuits, of R ^ and Rg. The armature lever en of the extra 
magnet is pallet shaped at its upper end, as shown. This pallet p, operates an es- 
cape wheel w, m.ounted on a ehaft s.' On the same shaft is carried a toothed 
wheel w'. Below the wheel w' is arranged a flat contact spring c, which, normally, 
rests against the contact screw c' This spring c, and screw c', are normally separ- 
ated, except at, or near, the contact point, by insulating material. The main line 
wire, it will be seen, is led to and through c and c' by the wires x, x', and that, 
when the contact at c c' is broken, the main line is opened. The spring c is extend- 
ed upward in proximity to the toothed wheel w'. When the armature lever en is at- 
tracted to and withdrawn from the electro-magnet em, the pallet p engages with 
the escape wheel w, and gives it and, consequently, the wheel w', a "step by step''* 
movement, in the direction of the arrow. The position of the spring c is so adjusted 
with relation to the wheel w', that, when the armature lever is on its back stop, 
the end of spring c rests in the spaces between two of the teeth of w'. "When the 
armature moves forward the pallet so moves w' that one of its teeth rests just be- 
hind c. When the armature falls back again that tooth engages with c and sep- 
arates it from c', opening the main line circuit. But, before the armature 
reaches its back stop, the tooth of w' releases c, and it snaps back against c', a^raiii 
closing the main line at that point. 



1^2 



AMERICAN TELEGRAPHY. 



Thus tlie line wire is only opened between c and c' at tlie '' break " of the 
main line circuit. The figure 131 represents the " line adjusting " apparatus at the 
moment of opening the key at x. 

Now, if there should be an escape at e, Fig. 131, it will only be necessary for 
the despatcher at t to keep liis relay adjusted so that it will be operated by 
the opening and closing of the key at x. When this is accomplished the batteries 
at X and Y, in addition to the regular opening at the key, will be momentarily opened 
at EN and en/ and, in consequence, no matter how low a tension l:he operator at a 
may have on his relay, the armature of Rg will fly back at the moment of breaks 
at EN, en'. 

FIG. 132. 




DELANY V'LINE ADJUSTMENT," OR " BREAK" REPEATER. 

The adjusting apparatus as it appears m practice is shown in Fig. 132. A switch, 
shown on the base board of the apparatus, is provided to cut out this portion of 
the "escape nullifier " from the main line and locals when the condition of the line 
does not require its use. 

This apparatus is also designed for application to long underground circuits, 
on which it would be placed in way offices, and at the opening of the circuit would 
be caused to momentarily ground the line, thus facilitating " clearing " the circuit of 
its static charge, thereby permitting more rapid signaling. 

The various parts of this apparatus are similarly lettered in Figs. 131 
^nd 132. 



CHAPTER X. 

AUTOMATIC TELEGRAPH REPEATERS, 

Automatic repeaters in telegraphy are used in intermediate offices to avoid relay- 
ing messages manually between points, when, for various reasons, it would be unad- 
visable or impracticable to transmit the messages over a continuous wire. 

One such reason is that the strength of current on a wire, as already stated, de- 
creases as the resistance increases, and as the resistance increases directly with the 
length of the wire, more than the ordinary amount of battery at the terminals 
would, therefore, be required to j^roperly work very long circuits. Another reason is that 
there is more or less " escape " of current at every pole on a line, in addition to the 
places where the wire comes into contact with house-tops, foliage, etc., and this escape 
of current from the wire to the earth, via these numerous routes, is greater as the re- 
sistance of the wire itself is increased. This is in accordance with the law that the 
amount of current in the branch circuits of " divided circuits " is proportional to the 
resistance of each circuit, {see " divided circuits.") Hence, it is advisable to keep the 
length of the wire within certain limits to avoid undue waste of current from that 
cause. Again also, the speed of signaling, or, in other words, the rate at which the 
circuit can be charged and discharged in order to properly operate the receiving in- 
struments, decreases as the static capacity of the wire is increased, and //z^/ capacity 
it is known, increases with, among other things, the length of the circuit. {See Distri- 
bution of Static Charge.) 

The function of the " repeater " is to take, as it were, the message from one wire 
and "relay" it, automatically, to another wire, thereby dispensing with the necessity 
for manual reception and transmission at the intermediate office. 

Morse, whose first electro-magnets for telegraphing were so constructed as to re- 
quire for their operation a much greater strength of current than do the relays of to- 
day, was the first to employ " repeaters " for relaying messages from one wire to the 
other, in intermediate offices, and he appropriately named the instrument he enn)loyed 
for this service the "relay." Subsequently, Morse devised the local sounder to be 
operated by the " relay," and this name has clung to the latter instrument. 

A name becoming necessary for the automatic " relaying" instruments, when they 
were first invented, and the term "relay " having been bestowed upon another instru- 
ment, the term " repeater," presumably came to be used as signifying apparatus which 
otherwise might have been termed a relay. 

It may be mentioned that the term "repeater" was employed in Great Britain, as 
early as 1837, to designate " a mechanical circuit breaker, which consisted of a forked 
wire made to vibrate in and out of mercury cups alternately." It was used in con- 
nection with a magneto-electric machine. Subsequent modifications of this device 
were termed " electrepeters." 

iJ3 



154 




/REPEATERS. 155 

Although apparatus for repeating automatically is now so plentiful, instruments 
capable of pei-forming that function, were, at one time, looked upon as something greatly 
to be desired; and, before the invention of the first " automatic repeaters," it was 
thought that a decided advance was made when *' button " repeaters were introduced. 

Button repeaters automatically repeat from one wire into another by means of a 
relay, but only in one direction, until a switch is manually turned at the repeating 
station, where an operator sits beside the repeaters, listening to what is passing, ready 
on the instant to turn a " button " Qver to permit one or other side of the repeater to 
break or send. 

BUTTON EEPEATERS. 

About the first button repeater employed was the " Woods," a diagram of which 
is given in Fig. 133. Its operation is very simple. 

The diagram represents the apparatus at the intermediate, or " repeating '' office, 
only, s, is the button switch. The lever /is pivoted as shown. It is composed of 
ebonite, or other insulating material, and carries on its lower edges two metallic strips 
c, c', one on each side, which are insulated from each other. On the base-board are 
four contact strips ^, b' ; ^, a' , When the lever /is turned to the left, the contact strip 
c, on its left side, connects the contacts b^ b\ and the contacts a, a' are separated. It 
may be seen that a short wire 2, shown in dotted lines, short-circuits the contact 
points x' of the repeating sounder Rs', when the lever s is turned to the left. A simi- 
lar short w^ire i short-circuits the contacts x on the repeating sounder es, when the 
lever / of s, is turned to the right, which act joins the contacts a, a' together. 

The eastern wire passes through relay k, to the armature lever of es' and thence, 
via the short wire 2, and via battery b', to earth. The western wire passes through r', 
to the armature lever of es, and is there shown open in the figure ; both relays r, r', 
being open. 

The switch lever /, in the figure, is turned to permit East to send to West, and 
thus every signal sent by the east will be repeated by the sounder rs into the western 
wire; the lever of es acting as a key to open and close the western circuit. On the 
other hand, the repeating sounder rs' (in the present position of the button switch), 
does, not open and close the eastern circuit, because of the wire 2 via the button 
switch, which gives that circuit a closed route to the earth regardless of the openings 
and closings at x' of Rs'. 

Should the West wish to " break " or to send, the attendant at the repeating office 
turns the switch s to the right, separating the contacts b, b\ and connecting contacts 
«, a\ which now gives the repeating sounder Rs' control of the eastern circuit, and, at 
the same time, renders the' repeating sounder rs unable to operate the western circuit, 
inasmuch as its contact points are short-circuited by the short wire i. 

The necessity for these short wires consists in the fact that but for their presence 
either of the line circuits, when once opened, would remain opened. To explain, sup- 
pose that, (as in Fig. 131, and ignoring, for the moment, the short wires i and 2,) the 
button switch, s, is turned to permit East to send to West. At the opening of relay r, 
repeating sounder rs will open. This will be followed by the opening of the western 
wire at the point x; then relay r' in the opening will open sounder rs', which breaks 



1^6 AMERICAN TELEGRAPHY. 

the eastern wire at x\ Thus, when the western operator again closes his key, he finds 
his circuit open and has no means of closing it. 

When the button switch s is placed directly in the centre, the control of the re- 
spective circuits is removed from the armature levers of the repeating sounders, and, 
hence, the circuits are, by that act, made separate and independent circuits. In such 
central position the strip c' rests on the contacts a, a' and the strip c on the contacts b^ b\ 

Automatic Repeaters. 

It will be apparent to the reader of the foregoing that the chief function of an au- 
tomatic repeater must be to automatically prevent the '-opposite " transmitter* (as, for 
example, es', in Fig. 133, which controls the eastern circuit) from breaking, for in- 
stance, the eastern circuit, when that circuit is repeating into the western circuit. 

We have seen that this is done in the case of the " button " repeater, virtually, 
manually, by the act of the attending operator in the repeating office in turning on the 
short-circuit i or 2 around the opposite transmitter, as required. 

The same function is performed, entirely automatically, in various ways, by " au- 
tomatic " repeaters, several of which may now be described. 

THE MILLIKIX REPEATER. 

This was one of the earliest repeaters introduced into the telegraph service, and 
it is still a standard repeater of the principal telegraph companies of this country. 

This repeater may, perhaps, be termed an automatic, electro-mechanical repeater, 
for, while electricity is the controlling force in the performance of its automatic func- 
tions, the ultimate action is mechanical, as will be seen. 

Fig. 134 is a theoretic diagram of the connections of the Milliken repeater, r and 
r' are the main line relays. em and em' are extra magnets, which, in practice, are 
supported on metal standards that hold them rigidly in their respective positions relative 
to the main line relays. The armature levers of the extra relays are pivoted at the 
top as shown, t and t' nre transmitters. The levers l l' of the transmitters are insu- 
lated from the tongues, x x', at points / /', and from screw posts f, f', by small pieces 
of hard rubber. 

The working of this repeater may, perhaps, be best described by assuming that 
the East is about to send. To that end he opens his key; that opens relay r' and 
its lever /' falls back, as in the figure, and opens the local circuit controlling the trans- 
mitter t'. As the latter instrument opens, it first breaks the local circuit of em at a' ; 
the retractile spring s of extra magnet em, at once pulls its lever against the lever /of 
relay R as in figure ; presently the transmitter t' opens the western circuit at .t'; this 
demagnetizes relay R, and its spring would withdraw its lever /, from its front stop /, 
thereby opening the transmitter t, and, consequently, the eastern circuit at^, but that, 
as already said, the lever of em is against lever /, holding it on its front stop and thus 
keeping the local circuit of t closed. When the East again closes his key, relay k' also 
closes, consequently, so does t'; this action closes em, and the lever of that instrument 
is withdrawn from its position against the lever r. This releases e's lever, but, as now 

* See Transmitter, (continuity preserving) Duplex Telegraphy. 




157 



II 



f>^ 



^ 



158 AMERICAN TELEGRAPHY. 

the western circuit is closed at x% the lever / is held forward by its armature. 

Ill this way the function of the repeater in keeping closed the opposite trans- 
mitter, and virtually also the circuit which is being "repeated '' into, is performed. 

Should the West now desire to '• break," or send to the East he opens his key,' 
which action, by opening the local circuit of transmitter t, at/, opens the eastern circuit at 
X. The East finding his circuit now open, closes his key to await the remarks of the 
West, when the "repeating" actions just described are reversed. 

The Milliken repeater is considered by many to be one of the best repeaters 
known , if not the best. A drawback, perhaps, being that it is somewhat diffi- 
cult to maintain in proper adjustment by the inexperienced. The local batteries 
which operate the extra magnets are termed " extra " locals. These require to be 
carefully looked after in order to secure the best results ; but this, it may be said, is 
also true — perhaps not to the same extent — of all " locals " and other batteries for 
all purposes in telegraphy. 

Side REPEATfeRS. — The Milliken repeater is also available as a "side" repeater. 
That is, assuming a through circuit between New York and Buifalo, via Utica, and 
that it is desired to repeat into a "side " circuit extending, for instance, from Utica to 
Ogdensburg; one side of the repeaters may be placed in the througli wire and the 
other in the '" side " wire, and thus whatever signals are transmitted on one wire are 
heard on both. To explain briefly how this is accomplished. If, in Fig. 134, we call 
the western wire the "side"' wire, and imagine the main battery b, controlled by 
transmitter t, to be cut off, and the wire running to ground at that battery to be 
"looped" out of the office instead, (as if //were the "through" wire) that will be all the 
change necessary. 

THE TOYE REPEATER. 

. This repeater is quite extensively used in the United States and Canada. It is 
quite simple in its operation. In Fig. F35 is to be found a diagram of its electrical 
connections, t and t' are the usual transmitters. These transmitters differ, however, 
from those used in the Milliken repeater in that they are not insulated at the screw 
posts. R r' are the usual main line relays, mb, mb', the main line batteries. rIi, and rIi', 
^.re adjustable rheostats, the use of which will shortly be explained. 

The manner in which the " opposite " transmitter is kept closed or passive, is as 
follows: (by " opposite " transmitter, it maybe repeated, is meant the transmitter 
which is controlled by the relay in the circuit which is being repeated into). 

Supposing again, that the East is sending to the West through the "repeaters." 
When the East opens his key, the relay e opens, as in the diagram; this opens trans- 
mitter T and, consequently, the western circuit is opened at x. At the 
same instant that the western circuit opens at x, the circuit which includes the relay 
r' and battery mb' is closed via the lever of transmitter t through the rheotat eIi. The 
resistance of the rheostat is adjusted so that it equals the resistance of the western cir- 
cuit. As this transposition of circuits maintains the current passing through relay r/ 
at the same strength as before the change of circuit was made, that relay remains 
closed and, likewise also, the transmitter t'. 



159 



g JI^|i|i|iK 




l6o AMERICAN TELEGRAPHY. 

It will be noticed that this automatic method of keeping the opposite transmitter 
closed is exclusively electrical. It need hardly be said that when the West wishes to 
send to the East the foregoing action is reversed. 

An advantage held by this repeater over the Milliken is that it dispenses with 
" extra " batteries and " extra " magnets. The Toye, however, is severe on the main 
battery as the latter is always kept closed in this repeater. 

In the practical operation of this repeater care must be observed to keep the re- 
sistance in the rheostat about equal to that of the main line, especially in bad weather: 
otherwise the signals may be uneven, due to the variation in the strength of current 
traversing the relay as its circuit is changed from that of the line to that of the rhe- 
ostat. 

This repeater is not available as a " side " repeater, since it requires the presence 
of a main battery to keep the relay closed at the proper time. 

:maver-gakdanier repeater. 

The above was the title this form of repeater went under in the Baltimore and 
Ohio Telegraph Co., where a large number of them was in operation. The writer has 
since been informed that this repeater was previously invented by others, (whose 
names are unknown), and that it was in operation in the Montreal office of the Mon- 
treal Telegraph Company a number of jesus ago. 

The "opposite " 'transmitter of this repeater, a diagram of which is given in Fig. 136, 
is automatically kept inoperative at the the proper time by the use of a device which 
(?pens its local circuit. The main line relays operate their respective transmitters by 
the back contact points. Consequently, the signals, as heard on the transmitters, are on 
the "back" stroke. The main line connections, however, on the transmitters, are so 
arranged that, when the transmitter is open, the main line passing through its contact 
points is closed, and vice versa. This is done by connecting the main battery wire to 
the lever of the transmitter instead of to the post p, as in "front "' stroke repeaters; 
hence, the signals are repeated from one line into the other on the "front " stroke, 
notwithstanding the "back contact" arrangement of the relays. The front contact 
point of each main line relay controls a local sounder, as shown in the figure; conse- 
quently, the operator in attendance can hear, not only how tlie signals come to him, 
but how they pass to the other side, without the necessity of going to the switch board 
to cut in and listen, which is an advantage not possessed, or at least not, to the writer's 
knowledge, utilized, in any of the repeaters herein previously described. 

The operation of this repeater is as follows: Supposing the East to be sending to 
the West. He opens his key, which action opens the relay, r. The armature lever of 
that relay falls back, closing the local circuit of transmitter t, via the lever of t' and 
the switch s.' When the transmitter t is closed its post p separates the tongue / from 
the lever L. This opens the western line at /; consequently, relay r' is next opened 
and its armature falls on its back contact. This does not operate transmitter t', how- 
ever, as the local circuit of that instrument was opened, at^ on transmitter t, the mo- 
ment that T started to close, and, thus, when the East again closes his key, r is at- 
tracted, and T is opened. When the West wishes to send, the foregoing actions are, as 



l5l 




1 62 . AMERICAN TELEGRAPHY. 

in the case of tlie other repeaters described, simply reversed, the transmitter t' keeping 
T, passive, by the opening of the local circnit of the latter at x.' 

The " 3-point " switches s s' are used to put the repeaters "through," or to separate 
the sets. 

In the management of these repeaters it is recommended that the adjustment of the 
relays be made by moving the magnets of the relays backward and forward. This 
insures a uniform stroke of the relay armature on its local contact in all kinds of 
weather. The local sounders s s' are utilized to give signals on the front stroke. 

The best manner of adjusting these repeaters is to ask one or other of the " re- 
peating " circuits to send. Suppose in this case it is the West. Listen at relay r and 
adjust relay e', and transmitter t', until the signals are heard perfectly at relay r; this 
will show that the repeating apparatus is doing its work correctly. Then have the 
East write ; listen at r' and adjust relay, r, and transmitter t, until the signals pass 
ok, when the repeaters are adjusted. When not required as a repeater the instru- 
ments may be used for ordinary Morse telegraphy, by turning the 3-point switches 
to the right, (whereby the transmitters are rendered inoperative,) and by having the 
proper wires run from relays to switch board to facilitate cutting them in. 

THE NEILSON REPEATER. 

This repeater is in use in Canada.* It is deserving of desoription, if for no othei 
reason than that of its uniqueness; it certainly bears no marked resemblance to any 
of the " repeaters " known to the writer. 

At first sight the repeater may appear a little complicated, but in reality it may 
be quite easily understood, although, it must be said, it performs its function of keep- 
ing the "opposite " transmitter closed, in a round about, if in an ingenious way. 

In Fig. i'37, r' and r are the regular main line relays; r' and r are extra relays of 
about 30 or 40 ohms resistance, each, s' and s are repeating sounders, or transmitters; 
s' having control of the eastern wire and s of the western wire, r' and r, by their 
armature levers, have control of s' and s respectively^. The wires of the local circuit lb', 
it will be seen, are extended from the lever /' and contact point x' of the relay r' to 
similar parts of the extra relay r, and the local circuit of lb is extended from the relay 
E to the armature lever and contact point of the extra relay r.' It will also be noticad 
that the local circuits lb' and lb are shunted into the magnet coils of the extra relays 
r' and r\ the reason for which will soon be plain. When the main line relays r' r 
are closed the coils of the extra relays are completely short-circuited by the points x 
and x' . 

Assuming the eastern office to have opened his key to send into the western cir- 
cuit; the relay r' opens and its armature falls back, as in the figure. This action opens 
sounder s', because of the resistance of the extra relay r', which reduces the strength 
of current in the sounder to such an extent that its armature is withdrawn. 

The same action, however, which has caused the opening of the sounder s' at 
once closes r\ which, owing to the greater number of convolutions of its coil, and more 
sensitive armature and retractile spring, requires a smaller amount of current for 

* It is now also in use quite extensively in the United States. 



164 



AMERICAN TELEGRAPHY. 



operation. The act of opening tlie sounder s' opens the western circuit at n'. There- 
by, relay E, in the western circuit, is opened. When r' closes it is seen that its arma- 
ture closes the local circuit lb at its armature contact point «', so that, although the 
relay R is opened, as said, when its circuit is broken at the point n' of the sounder s', 
nevertheless, the sounder s is kept closed, since the resistance of its circuit is un- 
changed, and it follows that the western circuit is kept closed at N"; all as in figure. 
When the West wishes to send to the East he reverses the forgoing actions, and 
it will then be the sounder s, which is opened, and the sounder s', which remains 
closed. 

THE WEINY REPEATER. 

This repeater is shown in Eig. 138. The opposite transmitter is kept closed at 
the repeating station by the action of an extra magnet added to the main line relays, 
the construction and operation of which are, briefly, as follows : The extra magnet is 
wound with two coils, through which a current flows from a local battery in oppo- 
site directions around the core, so that the latter is, normally, not magnetized. 



WEST To Switch 




FIG. 138. — THE WEINY REPEATER. 



When, however, one of these extra coils is opened the current in the other coil mag- 
netizes the core. The wire which is joined to both coils of the extra magnet goes 
directly to the positive pole of the opposite local battery. The other end of each 
coil passes to the other pole of the same battery, one coil by way of the left-hand 
post, and the other by way of the lever of the opposite transmitter, as shown. This 
lever is insulated from the left-hand j^ost when the transmitter is open. Conse- 
quently, when the left-hand transmitter is open, as in the figure, the circuit of the left- 
hand coil of the extra magnet of the eastern relay is open at the left-hand post of the 
western transmitter, and as a result thereof that extra magnet is magnetized by the 
current passing through the right-hand coil, and, hence, the armature lever of that 
relay is held against its front stop. Thus, for example, when, as in the figure, the 



REPEATERS. 



165 



West sends to thfi East, and, thereby, opens his key, the western relay in the repeat- 
ing office opens, and its armature lever falls back, opening the local circuit of the 
western traubinitter. As this transmitter opens it, first, breaks, at its left-hand post, 
the circuit of the left-hand coil of the extra magnet of the eastern relay, and, next, opens 
the eastern main line circuit at the right hand post. As, however, the armature of 
the eastern relay is kept closed, in the manner stated, by its extra magnet, the eastern 
circuit remains unbroken in the repeating station. 

The local battery, it will be seen, is also utilized to operate its respective trans- 
mitter. Often a local dynamo is used for this purpose. A button switch is placed on 
the base of each transmitter for the purpose of short-circuiting the main line contact 
points on the transmitter when it is desired to use the transmitter simply as a sounder 
ior the relay. 

THE HOETON EEPEATER. 

This repeater. Fig. 138a, has recently been introduced into practice. It is sim- 
ple in operation and is said to be efficient. The sending circuit is held closed at the 
repeating station by the utilization of the force of gravity ; the main line relays R, r', 
being tilted, as shown in the diagram, for this purpose. Each relay is provided with 
an extra electro ma^^fnet, as shown, the local circuit of which is controlled by the oppo- 
site transmitter. Normally these local circuits are closed. Normally also the attract- 
ive force of the main line relay, aided by gravity, is superior to that of the extra mag- 
net. Hence, so long as the main line is unbroken, the armature of each relay remains 





■ h 'TU'/W' ^ 



V 



! J^^^^-W. 



\x 




FIG. 138^7. — rilE IIORTON REPEATER. 



on its front contact point, which contact point controls the usual transmitter, as seen 
in the diagram. When, however, for example, the West wishes to send to the East, 
and, for that purpose, opens his key, and the relay R is thereby demagnetized, the 
extra magnet at once withdraws the armature, breaking the local circuit of transmit- 



1 66 



AMERICAN TELEGRAPHY. 



ter T. This transmitter at once opens, which act first opens the local circuit of the 
extra magnet e' and next opens the eastern main line at the left end of the trans- 
mitter. The opening of the eastern main line, of course, demagnetizes the relay r', 
but as the local circuit of its extra magnet is open, gravity retains the armature 
on its front stop and, hence, the local circuit of transmitter t' is not broken. 
Consequently, the western circuit is not broken at the repeating station. Of course, 
these actions will simply be reversed when the East wishes to send to the West. 
The adjustment of the relay and extra magnets, as regards their distance from 
the armature, is regulated by the screws shown at the respective ends of the relays 
and magnets. 



THE ATKINSON REPEATER. 

This repeater. Fig. 138^, which has been quite generally employed of late by 
the Western Union Telegraph Co., is somewhat like the Neilson repeater in the 

manner of its operation. 
N and n' are extra sound- 
ers which control shunt 
circuits around the con- 
tact points of levers I V 
of relays R r'. n is con- 
trolled by the local con- 
tact X of transmitter t, n' 
by local contacts x' of t'. 
T and t' are in turn con- 
trolled by armature-lev- 
ers I V of the main-line 
relays R r'. mb and mb' 
are the main-line bat- 
teries. The operation of 
the repeater is as fol- 
lows : In the figure West 
is repeating to the East. 
The act of opening the 
western line opens relay r' and its armature falls back, opening the local circuit lb' 
of transmitter t', whose lever in rising first opens at x' the local circuit of n', whose 
armature-lever at once rises and closes the shunt circuit of lb at d'. The next 




FIG. 1381^. ATKINSON REPEATER. 



REPEATERS. 



l66a 



instant the lever of t' opens the eastern circuit at c'. This opens relay R, whose 
lever / falls back, but this does not affect transmitter T, since its local circuit lb is 
closed at d' of is'. Thns the opposite transmitter is kept closed. When East sends 
to the West these actions are reversed, and the transmitter t' is kept closed by a short 
circuit at d on the sonnder N. 



THE GHEGAN- EEPEATER. 

This repeater, which is employed on some of the large railroad telegraph lines 
and elsewhere, is of somewhat recent invention, and has given good service. It is 
nnique in that the superposed extra armatures a a% Fig. 1380^ whose levers control 

FIG. 138^. 

WEST EAST 




GHEGAN REPEATER, 

the shunt circuits, receive their magnetism by induction from the armatures of 
transmitters T t' respectively. These superposed levers are pivoted at b b' inde- 
pendently of levers L l'. Owing to their position armatures a a' are magnetized 
more slowly than the armatures of T t', and also lose their magnetism more quickly, 
further, when necessary, the levers of a a can be retarded still more in their down- 
ward motion by increasing the pull on their retractile springs t t\ and, in addition, 
the time of breaking the shunt circuit is increased by the flat springs on aa\ which 
rise somewhat until they reach their stop pin, as the lever descends, which features 
are found of much utility on heavily escaped lines. 

The o])eration of this repeater is as follows: West is supposed to have opened 
his key to send. This has opened relay r', whose armature y' falls on its back stop. 
This opens local circuit lb' at x\ and t' then opens. Immediately the superposed 
armatures' rises, closing shunt circuit of lb at the contact on lever of ^/. Xext, 
armature-lever l' of t' opens the eastern circuit at s' , r . This opens relay R, whose 
armature Y falls back, opening circuit of lb at x, but this does not open trans- 
mitter T, as local circuit lb has been previously closed at a. If East were sending 
to West the foregoing actions would be reversed, the superposed armature of T clos- 
ing the shunt circuit of lb' at «, etc. MB, mb' are the usual main-line batteries.- 



66b 



AMERICAN TELEGRAPHY. 



West 



East 




__m- 




Ym 



-=-B 



OPEK-CIKCUIT REPEATER. 

The theory of the open-circuit method of operating Morse circuits is shown in 
Fig, 36. Normally, on these systems there is no battery to the line. AVhen it is 
desired to repeat from one such circuit into another an arrangement theoretically 
sliown in Fig. i38t/ is frequently employed. This is a modilication of the repeater 
as used in Eurone, as to the apparatus, but the principle in each case is the same. 
The^e repeaters are also used by the United States Signal Corps on submarine cables 
on which the single-current, open-circuit method is employed. 

In the figure, R r' are polarized relays, with a bias or retractile spring to kee]) 
them, when at rest, on 

the lower or ''dead" ^ fig. 138^. 

contact. Ordinary Morse 
relays could be used as in 
Fig. Tyd. T and t' are 
normally open repeating 
transmitters, operated by 
relays R and r' respect- 
ively. B b' and 1) y are 
the main and local bat- 
teries. The operation is 
as follows: Assume that 
the East is to send to the 
West. He closes his key, 
putting his battery to the 
linCo The current from 

his battery traverses relay R via lever T and contact c' . This current brings th* 
armature of relay R against contact x^ thereby closing the local circuit of battery 
5, which closes transmitter T, thus putting main battery B to the western line, as 
shown in the figure, through contact t and lever / of T, and thereby operates the 
distant western relay. When the eastern operator next opens his key his battery is 
Temoved from that line. Consequently the bias or retractile spring of relay R brings 
the armature-lever to the dead stop, opening T, thereby removing battery B from the 
western line and opening the distant western relay. Thus the openings and closings 
of the eastern circuit are reproduced in the western circuit. It will be seen that 
when lever I of T was closed by its local battery l it opened the circuit of r' at c, but 
this had no effect upon that relay, as it was already " open." 

Reversely, when the West desires to send to the East, and to that end closes his 
key, the current from his battery energizes relay r', by way of lever I and contact c 
(for at such times transmitter t must be open), and thus closes the circuit of battery 
y at x\ thereby closing transmitter t', which puts the main battery b' to the eastern 
line by way of contact f and lever /', thereby operating the distant eastern relay. 
Ordinary reading sounders can be placed in series with the transmitter magnets, and 
switches are used to separate the sets when not used as i-epeaters, jmd to enable the 
repeating station to converse with either of the terminal stations. These switches 
and sounders are omitted to simplify the diagram. 



1 



OPEN-CIRCUIT REPEATER. 



REPEATERS. 



l66c 



DOUBLE-CUERENT SINGLE-WIRE REPEATER. 

This repeater, a modification of the Varley repeater, is used on circuits where 
th9 double-current system (see page 287) is employed, chiefly in Europe. A single 
battery and a pole-changing key are generally used at the terminal stations, but a 
double or split battery like those shown at the I'epeater station B b'. Fig. 180, and 
operated by a pole-changing key, or by a single battery with an ordinary pole- 
changer, Fig. 151, could also be employed. 

The advantages of the double-current system for single-wire working are that it 
is speedier, that the receiving instruments are more sensitive than the ordinary 
Morse relay, and that the}^ require less attention than the latter, since any variation 
in current strength on the line affects both poles of the polarized relay similarly, 
whereas in the case of continuous current working a variation in the current 

FIG. 138/. DOUBLE-CURRENT SINGLE-WIRE REPEATER. 

r r 



,^J^t 




^IM'r 



iruVc 



H|l[rl|lK 



strength makes it necessary to increase or decrease the tension of the retractile spring 
of the Morse neutral relay. 

In the double-current system, for ordinary working, the apparatus iaJ set for send- 
ing and receiving by means of a manually operated three-point switch p, Fig. 138^, 
which, when turned to the right for receiving, places the main line directly to earth 
via the receiver pr, a polarized relay. At this time, key k being open, the batteries 
are open as shown. When the apparatus is to be set for transmitting, the same 
switch is turned to the left, which disconnects the receiver from the main line and 
also connects the negative battery to the back contact of the pole-chauging ke}^ K, 
the positive pole of battery being permanently connected to the front contact of key. 
It is therefore evident that a double-current single-wire repeater must perform this 
function automatically at a repeating station. The manner in which this is done is 



l66^ AMERICAN TELEGRAPHY. 

indicated in Fig. 138/, in which a double-current repeater is diagram matically 
shown. B b' are split or double batteries. SK Sr' are neutral relays, termed automatic 
switches, with armatures a a' at each end. PR and pr' take the place of the pole- 
changing keys referred to. They are polarized relays whose levers control the 
batteries B b' as shown, practically as do PR pr' in the Wheatstone duplex repeaters. 
Fig. 232. R r' are also polarized relays with retractile springs attached to their 
armature-levers, which springs hold the lever in a middle position between contact 
points as shown at x\ when no current is passing through the coils, lr is a leak or 
telltale polarized relay, used for the same purpose as the similar relays pr" in the 
Wheatstone repeaters (page 308). Adjustable resistances r r are interposed between 
the earth E and the leak relay. These resistances permit only a small portion of the 
line current to pass through the leak. 

It may be seen that R and r', in either position of their armature-levers, control 
the switch relays sr sr' respectively. Normally the armatures a a' of the latter 
are against their back contacts, as shown in the case of sr'. When a current passes 
through the coils of sr or sr', both armatures a a' are attracted, as at sr. For 
simplicity the switches for separating the eastern and western sets are omitted. 

The operation of this repeater is virtually as follows: Assume that the East has 
started to send to the West. He has closed his key, which puts a positive pole of his 
battery to line, the current from which passes through and reverses the polarity of 
relays R and pr. This current in passing, by way of lever a' of sr', through lelay R 
has brought the armature-lever of that relay against a contact point x. This, by 
means of local battery ^, attracts armatures a and a' of SR to their front contacts as 
shown. This action switches the western circuit from the relay pr' and puts the West 
in contact, via a\ with the lever of relay PR, which lever has just been brought into con- 
tact with the positive pole of battery b, as in the figure; the thin line of the battery 
conventionally representing the positive pole, the thick dash the negative pole, in 
these diagrams. At the same time the lever a of SR offers a branch circuit to earth 
via lever a of sr' and resistance r, through the leak relay lr, operating that instru- 
ment. It is obvious that the next opening of the eastern key will send a current in 
the opposite direction which will reverse the polarity of PR, causing its lever to move 
to the other contact, and thereby to place the negative pole of B to the western line. 
R is, of course, also reversed at the same time, and while its armature-lever is passing 
from one side to the other the local circuit of battery h will be open and the levers 
a a of SR will tend to fall back. But to prevent this action a shunt wire 5, having 
a resistance about equal to that of sr, is placed across the terminals of that relay, 
whose current of self-induction discharges through the coil s while the armature of 
R is in transit, this sufficing to hold the armature-levers a a' against the front con- 
tacts during that interval. Thus the switch relay sr is automatically kept in the 
desired position, while the East continues to send without intermission, or as long as 
he keeps his battery to the line. When he ceases sending he turns the switch p that 
places the receiver to line and removes the battery. When the West wishes to send 
to the East the foregoing actions are reversed, and sr', which is also supplied with a 
shunt-coil s\ becomes the automatic switch relay, and pr' the transmitting relay, send- 
ing out reversals of polarity from b' via the front contact a' of sr' to the eastern line. 
From what has been said it is evident that so long as the East or West is sending 
continuously the receiving terminal cannot break or interrupt, as at such times he 
has no control of the battery at the repeating station. At a pause of the trans- 
mitting station, however, the automatic switch gives the receiving station such 
control. Ordinarily, where these repeaters are mostly used it is not customary to 
break until the end of a message, at which time the transmitting operator is on the 
alert for interruptions, which he can detect by the telltale galvanometer usually 
placed in the circuit of such systems. {See G, Fig. 36.) At such times the trans- 



REPEATERS. 



167 



mitting operator sets his switches for receiving. For high-speed working a condenser 
which is shunted by a non-inductive resistance of about 5000 ohms may be phiced in 
series in each circuit between the receiving relay and the ground, or, for instance, 
between relays PR and R. 



Multiple Repeaters. 

It is occasionally necessary or desirable to be able to repeat from one wire into 
several wires, and automatic repeaters capable of performing this function are some- 
times called "three cornered" repeaters. This can be accomplished, for instance, by 
the use of several sets of Milliken repeaters; causing them to act as " side " repeaters. 
In other cases where this is done button repeaters are employed. In still other 
instances the transmitters are furnished with extra contact points, tongues, posts, 
etc., which render those instruments capable of acting as multiple repeaters. 
Mr. R. T. Edwards invented a multiple repeater on this general plan, which he 
termed an " Octuplex" repeater, by which eight circuits could be repeated into. 

The present writer has devised an automatic multiple repeater, shown in Fig. 139, 



FIG. 139. 




THK MAVER MULTIPLE REPEATER. 

which dispenses with extra attachments on the. transmitters, and which is practically 
unlimited as to the number of circuits to be repeated into; and each of the circuits 
thus repeated into is able by this arrangement to "break" the sending circuit, or ta 
send into all of the others circuits of an opposite series. 

The main line relays are operated on the backstroke, so far as the locals are con- 
cerned. 

By the use of "repeating" sounders, RS, rs', similar to those used on the 
"second" side of the quadruplex, with contact point on the up stroke, the signals 
are converted into straight " stroke," before the transmitters are reached. It will be 
seen that the repeating sounder RS is, by means of its armature lever n', given control 
of the transmitters t/ t^' T3', and that ks is given control of transmitters t^ t, t^. 
Also, that main line relays R,', R./, r/, ai'e, through their armature levers, given, 
control of repeating sounder, rs', and that relays Rj, R.^, Rg, in the same way, 



08 



AMERICAN TELEGRAPHY. 



have control of repeating sounder rs. That is assuming, in the case of the relays, that the 
local circuits controlled by their armature levers are not open at the j^oints •/' or ./' of 
the transmitters t^' or t^^, in which case, the control of the repeating sounders is taken 
from the relays, as in the figure at jc'. 

In the figure, three main line circuits, east, and three similar circuits, west, are 
shown. The main line circuits are controlled by the various transmitters, as shown. 
For instance, circuits No. ie, 2e and 3E, being controlled by tlie levers of t-^, Tg and 
Tg, respectively. 

By the use of this multiple repeater, as already stated, any one circuit of the 
western series may repeat into all of the eastern series, and any one of the eastern series 
may repeat into all of the western series. It will, shortly, be seen that the operation is 
very simple. 

Assuming that No. i east circuit is about to send to all of the western circuits. He 
opens his key, which action, by opening relay r^, closes the repeating sounder e s', as 
shown. The repeating sounder closing, opens the transmitters t^', Tg' and T3', and, 
consequently, opens also the western main circuits at c' c' c'. 

It is seen that the transmitters Tj^ and t^' are somewhat different from the other 
transmitters, the former being furnished with tongues and a local circuit connection posts 
jr, x'. t' and t^ are termed the " master " transmitters. 

At the moment the transmitter t'^ started to open, in response to the breaking of 
its local circuit at the point d', the local circuit of the relays e^, Eg, E3, was broken at 
x'. It thus follows that when, immediately afterwards, the western main line batteries 
are opened at c', c', c', thereby opening said relays e^, E2, Eg, the repeating sounder 
ES, is not affected, and it remains open as in the figure. 

In this way the automatic portion of the repeater service is performed. As in the 
case of "single" repeaters, when the West wishes to send to the East the foregoing 
actions are merely transposed. 

By the arrangement of the local circuits of the relays it may be observed that each 
of them has control of the repeating sounders, as already said, but, of course, they must 
exercise that control at separate times. It is clear that should either No. 2 or No. 3, 
east, desire to repeat into the western circuits it has equal control of those circuits 
with No. I circuit, as in the case described. It is also plain that not any of the western 
circuits hear what either of the other western circuits may transmit, and if one should 
break, the fact would only be apparent to the others by the cessation of the "sending," 
and the remarks in reply to the breaking circuit. 

It will be obvious to the reader on consideration that the novelty of this repeater 
consists chiefly in the arrangement of the local circuits. The local contact of the relays 
being on the back stroke it may be seen that the local circuit could be extended almost 
indefinitely to include new relaj^s of additional circuits. And an equal number of 
transmitters could be included in the circuit of the repeating sounders d and d', to 
control the main batteries of such circuits. But, of course, it does not happen very 
often in actual Morse telegraphy that more than two or three circuits require to 
be repeated into. The repeating sounder can be dispensed with when desired and 
the transmitters would in that case be operated directly by the relays. 



CHAPTER XI. 

DUPLEX TELEGRAPHY. 

By duplex telegraphy is meant tbe sending of two messages over one wire in op- 
posite directions, that is, one from each end of the wire, simultaneously. 

In this and other chapters throughout, the apparatus, battery, etc., at the near sta- 
tion will frequently be referred to as the "home " apparatus; that at the distant sta- 
tion, the "distant " apparatus. For instance, the " home " battery; "home" relay; 
*' home " transmitter, etc. 

It has been pointed out that in ordinary Morse, or single wire working, signals 
can only be transmitted by one station at any one time, because of the fact that the 
opening and closing of the circuit by any one of the keys operates all the instruments 
on the circuit. 




THEORY DIFFERENTAL DUPI^EX, 



To make duplex telegraphy possi])le, tlierefore,it is essential that the signals trans- 
mitted from the home station shall not interfere with the signals to be received at tliC 
home station, The home receiving instruments at each station must, consequently, be 
so constructed, or so placed, that, while ready to respond to signals from tlie distant 
station, they will not be responsive to signals transmitted from tlie home end. 

These requirements are met in several ways, but the two most important are 
known as the " differential " and the " bridge " methods. 

The differential method will first be described: 

DIFFERENTIAL METHOD. — Wc liavc sccu that the cffcct of au electric current How- 
ing in a coil of wire wound around a soft iron bar is to magnetize the bar. One e:i(l 
of the bar will be a north pole, and the other end a south pole, depending upon tlu^ di 
rection of the current. We have also seen that the streno'tli of the resultino' mao-iu'- 



I/O 



AMERICAX TELEGRAPHY. 



tism in the bar is, within the requirements of electrical telegraphy, proportional to the 
strength of current in the coil. 

In Fig. 140, B is a bar of soft iron, around which are wound two similar coils of 
insulated wire which, respectively, start from a common battery b, and are continued 
by wires i and 2 to the earth. 

It is a law of electricity that when the current has a choice of paths in which to 
complete its circuit, it divides in proportion to the resistance of each path {see Divided 
Circuits). In Fig. 140 the coils are shown wound around the bar in opposite direc- 
tions. The resistance of each wire, i and 2, attached to the coils, is the same, hence 
an equal amount of current flows through each coil from the battery to earth. Conse- 
quently, the current in coil i has a tendency to make one end of the bar a north pole, 
while the current in coil 2, being in the opposite direction around the bar, has an equal 



^-^ 




THEORY DIFFERENTIAL DUPLEX. 



tendency to make the same end a south pole. Hence, the bar is not magnetized by 
either coil, as the effect of one is neutralized, or balanced, by that of the other; quite 
as effectively, for instance, as one pound weight in one tray of a scales would balance 
another pound weight in the other tray. Or, it is, virtually, as if we should suppose 
that the cuiTcnt flo-sving in each coil should, with equal strength, tend to rotate the 
bar in its direction. As the tendency of the current in one coil to rotate the bar in 
one direction would be opposed by that of the cm-rent in the other coil to rotate it in 
the opposite direction, obviously the bar would remain at rest. 

Since, then, with equal currents flowing in these coils in opposite directions 
no magnetic effect is produced in the bar, it is clear that it is immaterial w^hether the 
current from battery b be flowing or not, so far as the bar is concerned. A bar of soft 
iron, or a relay, wound in the manner stated, is said to be wound " differentially," not 
because of the opposite winding but, rather, because, as we shallsee, they are operated, 
that is, magnetized, by differences in current strength in the respective coils. 

Suppose, now, that the bar B,in Fig. 141, represents a home relay of a duplex 
telegraph system, and that bar b' is the core of a distant relay, with but one coil shown. 
In order that equal currents from the battery at the home station shall still pass through 
the coils of e, a coil of ^vire r, equal in resistance to the line wire between b and b' 



DUPLEX TELEGRAPHY. 



171 



added to the distant coil around b', is placed in wire 2. The result is that, owing to the 
winding of its coils, b, at a, is not magnetized by the current from the battery at a, but 
as the current from that battery passes in one direction only around b' that bar is mag- 
netized. If, now, a key were placed in the circuit at k, and it should be opened and 
closed, the bar b would remain unaffected, as before, but b' would be magnetized and 
demagnetized, as in the case of a relay in an ordinary Morse single circuit. 

If then, differentially wound relays be placed at both ends of the wire, with a bat- 
tery, key and resistance coils at both stations, it will be found that neither of the re- 
lays will be responsive to its home battery, but that each will respond to the movements 
of the distant key, or transmitter, in a manner which may be understood by the aid of 
the following figures. 

In Fig. 142, B is an iron bar which may correspond to a duplex relay, at a. b' is a 
battery at a distant station in circuit i . The resistances of wires i and 2 are supposed 
to be equal. Battery b' is so arranged that its current coincides in direction with the 
current from battery b. It is assumed that the electromotive force of each battery is 
the same. The effect is that, the electromotive force in wire i being doubled, the cur- 
rent in wire i, and, consequently, in coil i, of the home relay, is doubledj while, as the 



FIG. 142. 




THEORY DIFFERENTIAL DUPLEX. 



electromotive force in wire 2 has not been increased, the current in coil 2 remains as 
in Fig. 141. This "excess" of current in coil i magnetizes the bar virtually as if 
there were but one coil with a current from one of the batteries flowing in it. This 
action will be referred to again. 

Should the battery at the distant end be so connected that its electromotive force 
opposed that at a, the result will be that no current will flow in wire i ; but, as tliere 
is no opposing electromotive force at the distant terminal of wire 2, a current will flow 
through coil 2 and wire 2 from the battery at a, and this will magnetize the core of the 
relay. From which it is seen that it is, in a sense, immaterial whether the batteries 
at the ends of the wire i, assist or oppose each other. In either case the operation of 
home relay will be due to the operation of the distant key. 



172 



AMERICAN TELEGRAPHY. 



The main feature of the differential method just described is that it prevents the 
home battery from affecting the home relays, by securing, so far as the home bat- 
tery is concerned, an equal flow of current through each coil in opposite directions 
around the core, but yet leaves those relays free to be actuated by the distant 
battery, which latter is, of course, essential. 

There is, as already noted, another method employed for the same purpose, 
namely, the ^'bridge " method which depends for its success in preventing the effect 
of home battery upon the home relay upon the maintenance of an equal and oppo- 
site potential, or pressure, at the terminals of the bridge wire in which the relay is 
placed. This method, which will now be described, is founded on the principle of 
the Wheatstone bridge. 



" BRIDGE " METHOD. — In Fig. 143 wircs I and 2, and battery remain as before. 
The coil around the bar b, representing the relay, is now shown connected betweeji 
wires i and 2. In this arrangement but one coil is necessary in the relay, a' and 
b' are resistance coils placed in the " arms" of the Wheatstone bridge. Assuming 

the resistance of these arms to 
^^^' ^43. be equal, and the wires i and 2 

also equal, the electric pres- 
sure, or potential, due %o bat- 
tery ^, at the terminals of the 
bridge wire must be equal and 
opposite, consequently, a cur- 
rent will, of course, not flow 
through the bridge wire, and 
hence the bar b, or relay, as in 
practice it would be, is not 
magnetized. 

This action may be ill- 
ustrated as follows : — Sup- 
pose in Fig. 143 the battery b^ 
at A, to be a water pump ; that the wires, or circuits, a ' i and b' 2 are parallel pipes 
of equal diameter and length and that they are connected, at equal points remote 
from A, by a pipe b. It is then obvious that if the pump b is caused to force water 
through the parallel pipes, no water will flow through b, inasmuch as the tendency 
to such a flow from either end of b will be offset by an equal and opposite tendency 
from the other end. But, if, by any means, the pressure at one of the ends of b be 
made less or greater than at the other, a current will pass through that pipe from 
the end of greater pressure. Such a difference of pressure at one of the terminals 
of B might be brought about, for instance, by the use of another pump at the dis- 
tant end of pipe i, which could, by assisting or opposing the flow of water through, 
that pipe, vary the pressure at B as desired. 

Analogously, in the case uf the bridge method, if a battery be placed in the 
circuit at the distant end of wire i it will cause the potential, or pressure, to vary so 
that a difference of potentials is brought about at the terminals of the bridge wire 




THEORY BRIDGE DUPLEX. 



DUPLEX TELEGRAPHY 173 

and a current will flow from the terminal of higher to the terminal of lower pres- 
sure. 

If then (as in the case of the "differential" method) each end of a duplex cir- 
cuit be equipped with the bridge arrangement, etc., it is clear that the variation of 
pressure at the terminals of the bridge wire, due to the operation of the distant 
keys, will effect an analogous result to that of the excess of current in one of the 
coils in the differential arrangement of the coils of the relays, namely, a current 
will flow in the coil and the core will be magnetized. 

In the single Morse system, as stated, when any one key is open it opens the 
entire circuit ; consequently, during that time, no other key can "operate" the circuit. 
It is clear that such a result following the opening of one of the keys in a duplex 
telegraph system would be fatal to success. Tliis result is avoided in duplex teleg- 
raphy by the use of keys, or transmitters, of peculiar construction, which will be 
described later on. 

There are two systems of duplex telegraphy quite generally used in this country 
namely, the Stearns duplex and the polar duplex. 

The Stearns duplex system is operated by " increase and decrease " of current 
on the line, or by placing the line to ground and to the battery, alternately. 

The polar duplex is operated by "reversals of polarity," obtained by alternately 
placing first one pole and then the other, of a battery, or other source of electricity, 
to the line. 

In the operation of these systems, as will be noted in the ensuing descriptions^, 
distinctly different apparatus is employed. They may be arranged on • either the 
** differential " or " bridge " plan. The differential is the one most frequently em- 
ployed in overland telegraphy; the bridge plan is almost invariably employed ia 
submarine telegraphy. 



174 AMERICAN TELEGRAPHY. 



THE STEARNS DUPLEX. 

The Stearns duplex is, broadly speaking, operated in practically the same way 
as is the ordinarj^ Morse telegraph system; namely, by the placing of a battery in 
the line to actuate or magnetize the home relay, thereby attracting the armature, 
and by removing such battery from the line, thereby permitting the retractile 
spring of the armature lever to withdraw it from the core of the relay. 

The home battery is prevented from affecting the home relay when the home 
key is opened and closed in the manner described as the '* differential," namely by 
winding the relays " differentially." This duplex is sometimes termed the differential 
duplex. 

In connection with Fig. 141 a coil of wire was shown inserted in the wire 2 to 
make the resistance of that wire equal to wire i, in order to insure that the current 
flowing in each coil of b should be equal. 

In actual duplex working in which the differential or bridge plan is utilized, it is 
similarly necessary that the resistance of the wires attached to the respective coils of 
the relays, or to the arms of the "bridge," should be equal, that an equal strength of 
current from the home battery should tend to flow in each coil , or wire. 

In the arrangement of a " differential " duplex, as the main line wire is connected 
to one of the coils of the relay at each terminal station it is clear that considerable 
"resistance'' must be connected up with the other coil to ensure that the current flow- 
ing in the latter coil shall be equal in strength to that in the former coil. It is clear 
also that, if, in duplex telegraphy it were necessary to provide a wire, similar in 
size and length to the main line wire, wherewith to bring about this equality of cur- 
rent in both coils , the main advantage of duplex telegraphy, namely, its ability to 
provide additional facilities for telegraphing without increased expenditure for wires, 
would be lost. 

But such, fortunately, is not the case, for it is well known that, with a given 
electromotive force and a circuit of a given resistance, the strength of current will be 
the same, whether the conductor composing the circuit be one mile or one hundred 
miles in length, one inch or one foot in diameter. 

Availing of this fact the resistance necessary to insure the eq[uality of currents 
referred to is made up of " resistance coils," composed of small wire of high resist- 
ance, termed a "rheostat," or "resistance box," which is constructed in such a man- 
ner {See Rheostat) that the resistance may be varied until it is found to equal the 
resistance of the main line. When this result is obtained the duplex is said to be 
" balanced." The method of obtaining this balance will be fully described. 

In Fig. 144 the connections and apparatus of a Stearns duplex system 
are shown, theoretically. Two stations x and y are represented and the instruments 
and apparatus at one station are duplicates of those at the other. 



^75 







X 





176 AMERICAN TELEGRAPHY. 

R and R' represent the resistance coils just referred to. In practice these coils 
are generally termed the " artificial " line; sometimes the compensating line. 

The coil of the relay at either end Avhich is connected to the main line is termed 
the " main line '' coil; the coil connected to the resistance coils, the " artificial line " 
coil. 

B and b' are the main batteries, t and t' are instruments known as " continuity 
preserving" transmitters but, ordinarily, termed simply, transmitters. These trans- 
mitters are operated by a local battery and Morse key, as indicated in the figure. 
Differential relays r and r' ^re placed at each terminal. 



CoNTTXUiTY PRESERVING TRANSMITTER. — The transmitter in the Stearns duplex 
takes the place of the key in the simple Morse system. It has, as may be seen (t, t' 
in Fig. 144) a lever l, which is bent at one end. The lever carries a piece of insulat- 
ing material m on which is fastened a strip of metal s,' generally of steel, called the 
"tongue," which extends nnder the bent end of the lever l. A metal post, or 
standard p, is equipped with a screw s, the lower end of which is near to, and in 
certain positions of l, touches the tongue s', making contact therewith, as at trans- 
mitter T. 

A Avire leading to the line is generally connected, as shown, to the tongue, the 
battery wire to the X30st p, and the " ground " wire to the lever l. Hence, when 
so connected, if the transmitter be " open " the line is placed to the ground, as at 
t', and if it be "closed," battery is placed to the line, as at t. 

The transmitter derives its name," continuity preserving',' from the fact that, by 
the arrangement of the tongue j' the screw ^ and the bent end of the lever l, the 
line wire which is attached to s' as shown, is transferred from the battery to the 
earth without any '' break " in the '^ continuity" of the circuit. This will be apparent 
from an examination of the diagram. In the figure the transmitter at x is closed. 
AVhen it ojjens the right end of the lever will descend, and, as it does so, the tongue 
s' will come into contact with the bent end of l, which will withdraw s' from s and 
bave it in the position shown at station y where the key controlling t' is open. 

Operation of differential duplex. — In Fig. 144, as just stated, the trans- 
mitter T is closed and t' is open. 

This places the positive pole of battery b to the line and leaves battery b' open, 
but places the line wire to the ground at y. 

The current from x divides in equal parts at .t, one part passing to the main 
line and ground at Y, the other to the artificial line r and ground. The result is 
that, since the current from battery b passes around the coils of r in equal and op- 
posite directions, no effect is produced upon that relay. At the distant end y, how- 
ever, the current only passes through line coil of relay r\ to the ground, and, con- 
sequently, that relay is magnetized and its armature is attracted. 

The statement that the current only passes through the line coil of the relay at 
T may be slightly qualified, since, while it is true that in the position of the trans^ 
mitters in the figure the bulk of the current will pass through that coil to the ground 



THE STEARNS DUPLEX. 177 

via transmitter t', it is the case also that a smaller portion of the current will pass 
through the artiticiai line coil of r' to the ground, via r' ; but, as in doing so it 
passes around the core of the relay in a direction similar to that in which the cur- 
rent traversing the line coil passes around the same core it only assists in the 
further magnetization of the relay. The amount of current which will flow through 
the artiticiai coil at this time depends upon the respective resistances of sc' and r'. 
The greater the resistance of sc', the resistance of k' remaining the same, the great- 
er will be the strength of current traversing the artificial line r'. If there were no 
appreciable resistance at sc', virtually no current would pass through the artificial 
coiL 

When the conditions are reversed and transmitter t' is closed and t is open the 
relay at y will not be affected by battery, b', while tlie relay at x will be operated. 

When both transmitters are closed simultaneously, thus placing a positive 
pole to the line at x, and a negative pole to the line at y, the effect will be 
that practically twice the amount of current will pass through the main line coils of 
the relays as will pass through the artificial line coils. 

This is due to the fact that the placing of both batteries to the line has doubled 
the electromotive force on the main line circuit, while, practically, only the electro- 
motive force of one battery is placed to the artificial line at each station. This 
gives a preponderance of current in each main line coil, owing to which the. cores 
of the relays are magnetized and their armatures are attracted. 

Hence, since, as we have seen, with the distant key open and the home key 
closed or open, the home relay remains open, it is obvious that it is practically imma- 
terial whether battery is to the line or not at the home station, so far as regards 
signals sent from the distant end. In other words, owing to the differential arrange- 
ment of the coils of the relays and the fact that each coil is part of a circuit of 
equal resistance, the home relay is only responsive to changes in the current strength 
due to the operation of the distant transmitter. The manner in which the changes 
are effected will be referred to at greater length in the descriptions of the polar 
duplex and quadruplex. 

Spark coil. — In Fig. 144 sc is a small resistance coil (often termed the spark 
coil) employed to compensate for the internal resistance of the main line battery, 
when the transmitter is open. The object in using this coil is to maintain a uniform 
resistance on the line, in either position of the transmitter. For instance, assuming 
the internal of a battery to be 300 ohms. When the battery is to the " line " this 
300 ohms is added to the resistance of the line, whereas when the transmitter is 
"open "it would not be, normally. Thus, without the resistance referred to, 
placed at sc it would likely occur that an unevenness of the signals would follow. 

Static compensating condensers. c,c' are condensers which are employed in 
duplex telegraphy to impart to the "artificial" line a "static" capacity equal to that 
of the main line. {See Static Charge.) 

The necessity for the employment of condensers in this respect may be 
explained as follows. 

As has been shown elsewhere, conductors, besides jjossessing "resistance" also 
possess the property of eiectro-static capacity. The electro-static capacity of over- 



17^ AMERICAN TELEGRAPHY. 

head telegraph conductors is very much less than that of underground, or submarine 
conductors, about as i to 23. This is mainly due to the proximity of the latter to 
the earth, and also to the specific inductive capacity of the insulating material of the 
cable. 

The effect of charging a conductor which has measurable electro-static Rapacity, 
is that, at the moment of charge a greater rush of current takes place into the wire 
than would be the case if the conductor were devoid of this quality. When the 
battery is removed and a route to the earth provided, the accumulated "charge" 
rushes out in a direction opposite to that of the charging current. 

The German silver wire of which the rheostats employed as the artificial 
line are generally composed {See Rheostat) has, normally, no appreciable "static" 
capacity; the consequence is that, (unless capacity is furnished to the rheostat) at 
tlie moment when the home battery is placed to the main and artificial lines, and 
also when the battery is cut off, a greater quantity of current, for an instant, flows 
tbrougli the line wire coil of the relay than flows through the artificial line coil, 
and when the line wire is of suflicient length, this excess of current is ample to cause 
a momentary magnetization of the core of the relay which tends to attract the arm- 
ature. Or, it might be that the excess of "charge" and "discharge" currents, due to 
the static capacity of the line, would tend to momentarily demagnetize the core and 
thus permit it to be withdrawn from its contact point. This will be discussed further 
under the "Quadruplex." 

The effects of these momentary current of static charge and discharge of the line 
upon the home relays are, on long lines, of such an injurious nature as to entirely pre- 
vent the successful reception of signals in duplex telegraphy when both stations are 
simultaneously transmitting signals, and, were it not possible to compensiite for this 
effect, not only duplex but also quadruplex telegraphy, and especially the latter, would 
be impracticable. It is especially true of quadruplex telegraphy, because of the much 
greater electromotive force used in that system than in duplex telegraphy; the static 
charge and discharge increasing in direct proportion with the electromotive force of 
the terminal batteries. 

The instruments used to impart to the artificial line the quality of electro-static 
capacity are the condensers referred to, c, c'. Fig. 144. One terminal of the conden- 
ser at each end of the line is connected to the artificial line, k, e', the other to the 
earth. The condenser is provided with an adjusting arrangement by means of 
which its capacity is increased or decreased until it is found to furnish current which 
exactly offsets that due to the static capacity of the line. When such is the case the 
line is said to be balanced for "static." In order to bring about this balance more 
accurately it is sometimes essential to use tWo, or even three, condensers, arranged 
in multiple and with a resistance coil inserted before each of them In Fig. 144 
such resistance coils se and sc' are shown placed between condenser c and c' and the 
artificial lines. 

Instances will be seen of two and three condensers in figures of the Wheatstone 
automatic system. 

The effect of the resistance coil is to retard and diminish the condenser charge 
and discharge to conform more closely to the actual conditions of the main line. 



THE STEARNS DUPLEX. 



1/9 
Stearns" 



Terminal connectioxs. — The actual connections and apparatus of a 
duplex at one station are outlined in Fig. 145. 

R is a "differentially " wound relay, each coil having a resistance of about 200 
ohms. In practice this relay is somewhat larger than the ordinary Morse relay, t is 
the transmitter operated by key k, and local battery b. Rh is the rheostat for artifi- 
cial line, c is the condenser, re the retarding coil of condenser, sc is the resistance 



FIG. 145. 




TERMINAL CONNECTIONS, STEARNS DUPLEX. 



coil which compensates for internal resistance of the main battery b. r is a 3-point 
switch useful in "throwing" the line to "ground" when a balance is desired by the 
distant end, but it is not so essential in the Stearns duplex as it is in the polar duplex, 
inasmuch as if the transmitter be open the line is tliereby grounded. 



i8o 



AMERICAN TELEGRAPHY. 



Stearns tkansmittek. — In Fig. 146 the Stearns transmitter is shown as in 
practice, l is the lever ; / is the insulating material on which the tongue, t, rests ; p 
is the supporting post, insulated from the brass base plate on which the standard of 
l^ver L rests. 



FIG. 146. 




STEARNS TRANSMITTER. 



Balancing stearns duplex. — In taking a " balance" on this form of duplex it is 
only necessary to ask the distant station to open his key. This opens his transmitter 
which places the distant end to "ground." Dots and dashes are then made on the 
liome key and the rheostat and condenser adjusted until a "balance" is procured, 
which will be when the home relay, its spring being placed at a very low tension, 
does not respond to the opening and closing of the home transmittero 



THE POLAR DUPLEX. 
The Polar Duplex. 



l8i 



This duplex involves in its operation, among other principles, this one, that, when 
a current of electricity flows in a coil of wire surrounding a soft iron core, the iron 
not only becomes magnetized, but also that its magnetic polarity depends upon the 
direction in which the current flows in the coil around the core. 



FIG. 147. 




For instance, if, as in Fig. 147, the current circulates around the core from left 
tonight, as indicated by the arrows, the left hand end will be a north pole and the 



FIG. 148, 




right end a south pole. If from right to left, as in Fig. 148, the right hand end will 
be a north pole and the left a south pole. This will be the case regardless of the 
shape of the core. {See Polarity of Electro-magnets, page 201). 

It is known that the north pole of one magnet will attract the south pole of 
another magnet,and vice versa, and that the south pole will repel a south pole and a 
north pole a north pole. In Figs. 149 and 150 the north pole of a freely suspended 
permanent magnet a is placed between the poles of an electro-magnet r. The direc- 
tion of the current around e, in Fig. 149 is, as indicated by the arrows, such that its 
north and south poles are as marked, and, consequently, a is attracted to the right. 
In Fig. 150 the current is in the opposite direction around r, and its poles, it will 
be seen, are the reverse of those of k. Fig. 149, with the result that a is attracted to the 
left. 

Assuming the end of the permanent magnet a to remain of north polarity it 
is evident that, if the direction of the current around the coils be reversed repeatedly, 
A will vibrate from pole to pole in response to to tlie reversals. In such a case the 
permanent magnet may be considered the armature of the electro-macvnet and, by 
having suitable means for reversing the direction of the current in a circuit of which 



l82 



AMERICAN TELGRAPHY. 



the coils in Figs. 148 and 150 might form a part, it would then be easy to cause ar- 
mature A to operate a local circuit at each reversal of the current. 

The instruments and apparatus presently to be described, for so reversing the 
direction of the current and for responding to such reversals, constitute the more 
important instruments of the polar duplex. 

In this duplex, in overland telegraphy, the " differential " plan is generally adopted, 
to avoid interference with received signals by the operation of the home transmitter. 



FIG. 149. 



FIG. 150. 




Operation of pole-changer. — In Figs. 151 and 152 apparatus is shown for 
reversing the direction of the current. In those figures pc is a pole- changing trans- 
mitter, commonly termed a " pole-changer," designed to transpose the position of 
the poles of the battery as regards the circuit in which it is placed, and, consequent- 
ly, to reverse the direction of the current in the circuit. 

This pole-changer PC is of the class known as continuity preserving pole -chan- 
gers, and which are designed to "reverse" the battery with the least possible break 
in the circuit. In Fig. 151 the contact points are purposely separated more widely 
than is customary in practice. 

PC consists of a lever l carrying the armature a of an electro-magnet e; the latter 
being controlled by a key, k, and local battery b. The lever l is extended, as shown 
and has a platinum contact point p at- the end of the extension. Opposite p is another 
contact point p', supported by framework, not shown in Figs. 151 and 152, but seen in 



THE POLAR DUPLEX. 



183 



Figs. 157 and 158. Metal strips /, /', with platinum contact points, are also supported 
on the framework and pivoted as indicated. / is given a downward tendency, /' an 
upward tendency, by springs or otherwise, p' is fixed rigidly in its place. The poles 
of battery b are connected, respectively, to levers / and /', as shown. 

In Fig. 151 the pole-changer is shown closed. In that position the contact p is 
in contact with /, while p' is in contact with /'. This, it will be seen, places the neg- 
ative pole of battery b to the line, and the current on the line is in the direction in- 
dicated by the arrow. 

When the key, k, is opened, the extension of l is caused to descend. As it 
does so the strip /follows p until it is stopped by the contact point p'. p then severs con- 
nection with / and, descending still further, makes contact with /', which it pushes away 
from p', the whole assuming the position shown in Fig. 152. The positive pole of 
the battery is now placed to the line and, consequently, the direction of the current 
is reversed on the line, also as indicated by the arrow. 



FIG. 151. 




In Fig. 75 2 a relay, pr, corresponding to R in Figs. 149 and 150, is shown as at 
a distant end of the line. Its armature controls a sounder s. It is plain that as 
often as the battery is reversed by the pole- changer the direction of the current 
in the coil of r will also be reversed and, consequently, the armature a ndll be oscil- 
lated from one side to the other. Hence, by proper manipulation of the pole-chano-er, 
dots and dashes will be received at the distant station. 

In some countries this method of transmitting signals is used almost exclusively 
on single wire^. It is known as the " double current' method. The difference be- 
tween this and the Morse, or single current method, is that, in the double current 
method, the spaces are made, in reality, by placing that pole of the battery to the 
line which will cause the withdrawal of tlie armature of pr from its local contact 
point, while, in the Morse method, the space is made by opening the circuit, tlius 
cutting off the battery from the line. {See j^ages 2S7, 288). 



1 84 



AMERICAN TELEGRAPHY. 



Polarized relay. — The instrument corresponding to r in Figs. 149, 150 and 
PR in Fig. 152, and which is designed to respond, at a distant station, to the movements 
of a pole-changer at a home station, is termed a "poh\rized" relay, or, for short, a 
*' polar" relay. 

One form of this instrument, very generally used in duplex and quadruplex teleg 
raphy, is shown in Fig. 153. It is known as the Western Union polarized relay. 



FIG. 152. 




The polarized relay is a combination of a permanent magnet and an electro- 
magnet. The electro-magnet consists of short cores made of the best Norway soft 
iron, surrounded, (when intended for differential duplex Avorking,) by ';' differentially 
wound " coils, each having a resistance of about 400 ohms. In some forms of po- 
larized relays the core of the electro-magnet is extended beyond the edge of the 
coils so as to bring the poles face to face. These extensions, which are also of soft 
iron, are termed pole pieces, (See p,p, Fig. 154.) 

A permanent magnet, pm. Fig. 153, bent to the shape shown, rests on the base 
board of the instrument. These permanent magnets are formed of steel and are very 
retentive of magnetism. On the lower end, s p, of the permanent magnet the cross- 
piece of the electro-magnet rests. The cross-piece of the electro-magnet is a strip 
of soft iron connecting the two cores of the electro-magnet in the usual way. To the 
upper end, n p, of the permanent magnet,is pivoted, at x, a soft iron tube,, a, which 
extends between, and somewhat beyond, the poles of the electro-magnet. This is 
the armature of the polarized relay. This armature is constantly magnetized by 
its nearness to the permanent magnet pm. Assuming the end, n p, of the jDerma- 
nent magnet, to be its north pole, and s p its south pole, the armature a will be mag- 
netized so that its end between the poles of the electro-magnet will be a north pole; 
and the ends of the cores of the electro-magnet, which are also magnetized by 



THE POLAR DUPLEX. 



1S5 



contact with the permanent magnet, will be south poles; that is, during the time 



is flowing through its coils. 



The term maccnetizins 
differential ' ' 



that no " magnetizing " current 

current is used here, advisedly, because of the fact that, in a "differential" relay, 
the current does not magnetize the core until an excess of current flows through one 
of the coils. 

When, therefore, there is no magnetizing current in the coils of em, the arma- 
ture A, which, having no retractile spring, when placed exactly in the " centre " be- 



FiG. 153. 




W. U. POLARIZED RELAY. 



tween the two ends of em, will be attracted equally by both ends, since a south 
pole on each side is "pulling" with equaf strength, at a north pole. 

But, if the armature be placed nearer one* pole face of em than the other, it 
will be held towards that face, or end. Consequently, under the conditions stated, the 
armature will stay on whichever side it is last placed. When, however, a magnetiz- 
ing current passes through the coils of the electro-magnet, the magnetism in its core, 
(due to the permanent magnet,) is either increased or overcome and its ends become 
nortli or south poles according to the direction of the magnetizing current, and 



l!:» 



i86 



AMERICAN TELEGRAPHY. 



armature a is attracted by the south pole of the electro-magnet and repelled by the 
north pole. 

The magnetism of the electro-magnet of the polarized relay changes in re- 
sponse to the reversals of the distant battery and the armature yibrates to and fro 
between its front and back stops in accordance with those changes. 

It is obviously essential that the magnetism of the permanent magnet should not 
be reversed by the reversals of magnetism of the electro-magnet, otherwise tlie 
magnetism of the armature a would be reversed also and would fail, in thaf case, 
to respond properly to the reversals of the distant battery. Since the armature does 
respond properly, it is evident that the permanent magnet is not naaterially affected 
by the magnetic reversals of the electro-magnet. There may be a slight tendency to so 
change on the part, as it were, of the electro-magnetism of the electro-magnet, but, 
owing to the point at which the permanent magnet is connected to the cores or cross - 
j)iece, of the electro-magnet, that is, at its ''neutral" point, namely, at the middle of 
the cores, any such effect is not perceived in practice. 

The play of armature of the Western Union polarized relay is adjusted by 
means of the small screw s'. Its position between the cores of the electro-magnet 
is regulated by the position of the front and back contact points ^, c' . These con- 
tacts ride in a carriage which is movable, within certain limits, in the cylinder, R. 
The carriage is movable, back and forth, by the screw h. The armature may be 
placed directly in the " center" between the two poles of the electro-magnet by the 
movement of the screw h. The cores of the relay may be independently moved to 
and from the armature by the screws, x, x'. 

FIG. 154. 

, A form of polarized relay, a modi- 

€ fication of what is known in Europe 

as the Stioh relay, now the standard 
of the Western "Union Company, is 
shown in side Tiew Fig. 
154. Its chief working 
parts are enclosed in a 
brass case with an ebo- 
nite top in which there 
is an opening- 
through which 
the armature lev- 
er comes. There 
is also a small 
opening in the sides of the brass case through which the pole pieces of the electro-mag- 
nets can be observed for purposes of adjustment. In the figure this opening is enlarged 
in order to show more clearly the relative positions of the coils e e', pole pieces, etc. 
In this relay an ordinary horseshoe magnet is emploj^ed as the permanent magnet. It 
lies horizontally under the base b of the relay, as outlined in Fig. 154 a, which is a 
top view of the relay. The relay has two electro-magnets with separate cores, practically 
similar to those of the Wheatstone relay shown and described, pages 303, 315, 317 ; the 
main difference being that in this form the electro-magnets lie horizontally, length- 
wise, with pole-pieces facing, and the armatures are vertical, lengthwise, the lower 
ends of the armatures being loosely inserted in a recess in short iron extensions (x 
Fig. 154) from the respective ends of the permanent magnet by which the armatures 
are inductively magnetized. The pole- pieces extend across the ends of the coils, but 




THE POLAR DUPLEX. 



<S7 



FIG. I54rt. 



FIG. 1543. 





are connected to the cores as indicated. The pole- 
pieces and coils are moved to and from the arma- 
ture by means of the adjusting screws s s'. The 
local contact point and back stop c c' are movable in -<> 
a frame which is adjustable by the screw h. The mov- 
ing parts of this relay are much hghter than in some of those previously in use by 
this company ; the light, non-magnetic metal aluminum being used wherever practi- 
cable. As intimated, the relay has two separate armatures which, however, are carried 
on a common frame, which is outlined in Fig. 154 b. This frame is pivoted at/*/*. 
A A are the soft iron armatures. A6 is the armature lever, also of aluminum. 

Theory of the polar duplex. — The theoretic connections of a polai duplex at 
two stations x and y are shown in Fig. 155. In this, p c and p c' are the pole-chan- 
gers. P R and p r' are differentially wound polarized relays, b and b' are main 
batteries. 

E, r' are rheostats, or coils of insulated wire, adjusted to equal the resistance 
of the main line wires. This, it has been explained is necessary in order that, when 
the distant end is " grounded," the same amount of current shall flow through each 
coil of the differential relays, which will be the case w^hen the resistance of the rheo- 
stats equals that of the main line. 

In Fig. 155 the pole-changers at both ends of the line are open. This places the 
positive pole of batteries b and b' to the line. As these batteries are supposed to 
have an equal electromotive force no current flows over the main line. But a current 
from the respective batteries B, b' flow^s to "ground,'' via the artificial lines, in a 
direction which so magnetizes the cores of PR and PR' that their armatures are with- 
drawn from their local contact points, thus leaving the sounders open. It may, per- 
haps, be useful to explain these statements. It has been shown (Wheatstone 
Eridge) that when the terminals of a wire are at similar potentials, no current wall 
flow in that wire. In the case in point, when positive poles of equal electromotive 
force are placed to the main line at each etation it is j^lain that the terminals oi' 
that wire are at similar potentials. In the case of the artificial wires, on the other 
hand, the dista7it terminal of each is at zero, under w^hich conditions, of course, a 
current will flow in these wires. 

If now the pole-changer p c' at y, be closed, it will place a negative pole t(» 
the line. 



That action should reverse the magnetism in p r but should have no effect 



on 



the relay p r' at y. That such is the case we shall see. It is here suggested to 
the student that he draw diagrams to show these changes, inserting arrows to indi- 
cate the changed direction of the current. 



THE POLAR DUPLEX. 189 

With the positive pole to the line at x and the negative to the line at y there 
will be twice the current flowing over the line Avire that flows through the artificial 
lines. Before the reversal of p c' the current was flowing only through the artificial 
line coil ofpR, shown by the arrow, etc. After the reversal that current continues to flow, 
but now there is a current of twice its strength flowing in the main line coil around 
the core of p R in an opposite direction. The result is that the magnetism of the 
core of p R is reversed and the armature, a, is moved over against its local contact 
point, closing the local circuit. So far the result desired is brought about. Now 
let us see whether the polarized relay, p r', at y, has been affected by the action 
which has reversed the polarity of p r at x. 

Before the reversal of p c' a current was flowing only through the artificial line 
coil of p r' in the direction shown by the arrow. After the reversal of battery b' 
twice the current flows through the main line coil that flows through the artificial 
line coil, but its course through the main line coil is in the same direction, around 
the co7'e of p r', as was the current which previously flowed through the artificial 
wire coil, so that the magnetic polarity of p r' remains unaffected and its sounder 
continues open. 

If the pole-changer at x should also be closed that action will place a negative 
pole of battery b to the line. The result will be that, since the pole-changer at y is 
also closed, the negative pole of b' is to the line, consequently, no current will flow 
over it. But now the current through the artificial line coil is in an opposite direc- 
tion around the core to that which had made its magnetism north and south as mark- 
ed at its poles in the figure, and, hence, its magnetism is changed and the sounder is 
closed. It will also be found on examination that this reversal of the battery at 
X has not affected the relay at x although the magnetizing current has been trans- 
ferred from the main line coil to the artificial line coil. From all of which it is 
evident that, with a proper ''resistance" and "static " balance, the home relays will 
not have their magnetism changed by reversals of the home batteries, regardless of 
whether the poles of the batteries at the respective ends of the wire oppose or assist 
each other. 

BALANCING THE POLAR DUPLEX. 

The polar duplex is balanced by asking the distant station to " ground. " This 
he does by throwing the 3-point switch s, Figs. 155 and 156, to the left. (Some- 
times the left hand lower " point," or disc, is connected to the earth, via s c; sometimes 
it is the right hand lower point that is so connected.) This action disconnects the 
pole-changer and battery from the line and transfers the latter to the earth, via the 
resistance coil s c or s c'. These resistance coils are inserted, as in the Steams 
duplex, to compensate for the internal resistance of the battery at each end. When 
the distant switch has been turned the home switch is also turned similarlv. The 
adjusting screw k, Fig. 154? of the polarized relay is turned forward or backward until 
the armature remains on whichever side it may be placed. The home battery 
is then placed to the line by turning the switch s to the left. Then the pole-chan- 
ger is opened and closed and the resistance in r or r' is adjusted until the armature 



190 



AMERICAN TELEGRAPHY, 



of the relay remains on either side, as before. This insures a "resistance" balance. Tlie 
pole-changer is now closed and opened rapidly and if short clicks are heard the 
capacity of the condenser is varied until these disappear altogether. This shows 
that a " static " balance has been obtained. A static balance can also be got by 
asking the distant station to " cut" in, which he does by turning the switch to the 
right. When he has done so ask him to close his key so that the armature of the 
home relay will rest against its contact point. The armature may then be given a 
slight bias away from its contact point and the home pole-changer again operated. 
If clicks are still heard in the sounder, the condenser and its resistance coil are ad- 
justed until they disappear, when the distant end may be asked to write a few words 

FIG. 156. 



Pole C^a/r/7e/\ T ^ 



Zocal. 




-I Polarized Rela^ 




)4 ^y^ ^1 






Cands^er 






Lt OOOOOQ 



000000 



P/ieosfat/ 



E 



POLAR DUPLEX TERMINAL CONNECTIONS, (GRAVITY BATTERY. 

to give an opportunity to readjust the armature to its proper place. As a rule, how- 
ever, a good, working static balance can be obtained on a polar duplex without 
giving the armature of the polarized relay a bias. 

A diagram of actual connections of a polar duplex "set " at one station, is given in 
Fig. 156, with a gravity, or other chemical battery, as the source of electromotive 
force. The dotted lines represent the small wires connecting the apparatus to the 
binding posts. In the figure the polarized relay is shown with front and back 
local contact points, leading to screw posts 6 and 7, respectively. The j^olar relay is 



THE POLAR DUPLEX. 



191 



not always equipped in this way; binding post 7 being generally omitted. But the 
former arrangement is often useful, as it affords an easy means of putting the sounder 
on the "front stroke " when the distant battery connections are reversed, which fre- 
quently happens in practice, c R is the condenser resistance, a s is a 3-point switch 
used in " grounding " the line, sc is a "spark coil," or resistance box, adjusted to 
equal the internal resistance of the main battery. The other instruments are as marked, 
w. u. POLE-CHANGEK. — The Western Union standard pole-changer for gravity 
batteries is shown in Fig. 157. The contact points of the instrument are enclosed in 
a circular, glass-encased box. The end of the lever l is seen extending into the box 



FIG. 157. 




W. U. POLE-CHANGER. 

through an aperture in the back of the framework. The tension springs s, s' are in- 
sulated from the box. The contacts c c' are attached to the framework. The poles of 
the battery are generally connected to the springs s s' by way of their respective 
binding posts on the side of the base board. The lever is connected to the earth, and 
the contact points c c' to the line, or vice-versa, as desired; also via the bindiu^^ 
posts. 

B. AND o. POLE-CHANGEK.— In Fig. 15S is showu another form of pole-changer that 
has been and is extensively used. It was designed to afford ready access to the contact 



192 



AMERICAN TELEGRAPHY. 



points for cleaning and adjusting purposes, s s', c c', and l correspond to and 
perform similar functions to those of similar parts of Fig. 157. 

TERMINAL CONNECTIONS AND APPAEATUS OF POLAR DUPLEX WITH DYNAMOS AS SOURCE 

OF ELECTROMOTIVE FORCE. 

Fig. 159 shows connections of duplex with dynamos as generators of electro- 
motive force. A special form of pole-changer, p c, is employed when the electro- 
motive force exceeds the point at which " sparking " would occur at the " continuity 
preserving " contact points of the ordinary form of pole-changer, pc consists o^ 




B. AND O. POLE-CHANGER. 



the lever l, pivoted on trunnion bearings at x. p, p', are brass standards connected, 
respectively, to the positive and negative dynamo machines. The line wire is con- 
nected to the lever. The lever rests on p when closed, and on p' when it is open. 
Between its opening and closing there is a brief break in the circuit, scarcely per- 
ceptible at the distant end, and yet sufficient to perceptibly diminish sparking at the 
contacts. In other respects the connections are practically the same as when gravity 
battery is employed. 

p R is a polarized relay, c r is the condenser resistance, c is a static compen= 
sating condenser, r is the compensating rheostat, or artificial line, resistance. A s is 
a 3 -point switch, used in going to ground for a balance. More frequently a 
special form of switch is used in connection with the cutting oif of the dynamos. 
It is shown in the description of the Field quadruplex key system, d, d', are dynamo 
machines, r, r', are the resistances inserted to reduce spark at Dole-changer, etc. 

s c is a resistance equal to the resistance r, or r'. 




POLAR DUPLEX TERJJlNAL CONNECTIONS (DYNAMO KKV SYSTEM. 



CHAPTER XII. 



QUADRUPLEX TELEGRAPHY. 

A quadruplex telegraph system is one by which four messages may "be trans- 
mitted over one wire at the same time, two from eacli end, simultaneously. 

There are several " multiplex" systems extant by which two, four or more mes- 
sages may be simultaneously transmitted over one wire, but as a rule the term 
multiplex is applied to systems of the multiplex synchronous order {see the opening 
remarks of chapter on synchronous multiplex telegraphy, page 336), while those muiti- 
jjlex systems in wliich dot and dash signals are transmitted on a practically unbroken 
wire, by comparatively continuous currents, and which are received by rela} s in a man- 
ner virtually similar to that in which signals are received by the Morse relays, are 
termed "duplex" or ' quadruplex" systems. Of the latter, numerous different forms 
liave been devised. 

THE EDISON QUADRUPLEX. 

In this system the principles of the Stearns duplex and the polar duplex are 
combined on one wire. 

The Stearns duplex, as we have seen, is operated by the putting on and takirg off 
of battery from the line at the home station, which action effects the operation of a 
relay at the distant station. The polar duplex is operated by the reversals of polarity 
of a battery at a home station, which reversals are responded to by a polarized relay 
at a distant station. 

In the quadruplex system, the Stearns duplex relays respond to an increase and 
decrease of current on the line, regardless of the polarity of the current. The polar 
duplex relays respond to the reversals of polarity, regardless of the strength of current 
on the line. If, therefore, an arrangement be effected whereby instruments to cause, 
and respond to, an increase and decrease of strength of current, be combined, on the 
one wire, with apparatus for causing, and responding to, reversals in the direction of 
the current, it is evident that it would be possible to send two distinct sets of signals 
from one station; and then, by using, say, differentially wound relays to prevent in- 
terruption of received signals by the home transmitter, two messages could be sent at 
one time from each end of the wire. 

The quadruplex referred to employs in its operation a combination of 
apparatus similar to that just outlined; the chief instruments used in the combination 
being the transmitter, and a modification of the Morse, or neutral relay, of the 
"Stearns" duplex, and the pole-changer and polarized relay of the polar duplex. 

194 



THE QUADRUPLEX. 



195 



As herein stated, the differential winding of the relay prevents the operation of 
the home relays by the home battery, which is correct as far as signals transmitted 
from the home station are concerned, but it will be found that, in the beautiful and 
intricate actions that are continually occurring during the operation of the/////quadru- 
plex, the signals transmitted from the distant station are frequently made by the home 
battery. This will be alluded to in detail later. 

Theoky of the Quadkuplex. — There are several ways in which the forgoing men- 
tioned combination of the principles of the Stearns duplex and the polar duplex may 
be effected on one wire. One of these is shown, theoretically, in Fig. 160. PC is a 
pole-changing key; neIs a Morse relay; pr is a polarized relay; t is a transmitter, 
which, when open, inserts in the circuit, a resistance r; when closed, it short-circuits 
that resistance. 



FlG. 160. 



jyrn 



PR 




The result of introducing the resistance into the circuit is that the current strength 
is decreased. When the transmitter is open and the strength of current is thus de- 
creased, the spring of the relay, nr, is so adjusted that its armature is withdrawn fi-om 
the front stop, but when the resistance, e, is short-circuited, as in the figure, 
the consequent increased strength of current causes the armature to be attracted 
to the front stop. It is then apparent that if the transmitter be operated in the ordi- 
nary manner dots and dashes will be repeated by the relay nr. 

When the pole-changing key PC is operated, a positive and negative pole of 
the battery are alternately placed to the line. This has the effect of reversing the 
magnetism of the polarized relay and of operating its armature in the manner de- 
scribed in the chapter on the polar duplex. 

It is clear, that the only effect upon the polarized relay of increasing and de- 
creasing the current passing through it is that its armature is attracted more or 
less strongly to whichever side it may be at the time of increase and decrease; it 
being understood that the minimum current is made sufficiently strong to properly 
operate the polarized relay. 



196 



AMERICAN TELEGRAPHY. 



On the other hand the armature of the Stearns relay is attracted by both 
poles of its core when the current is sufficiently powerful to overcome the re- 
tractile spring. Consequently, the transmitter and the pole- changing key may be 
simultaneously operated and the former will operate the relay kr, but will not 
operate the polar relay; contrariwise, the pole-changing key will operate the polarized 
relay, but not the Stearns relay. 

It may be mentioned here that the reversals of magnetic polarity have a cer- 
tain effect upon the armature of the Morse relay nr during the time that it is 
attracted by the full strength of current but, in practice, this effect is rendered 
harmless by various devices, some of which will be referred to subsequently, and, 
for the present, the effect may be overlooked. 

The method just described. Fig. 160, has been chosen to illustrate the 
theory of the combination on one wire, of increase and decrease of current and re- 
versals of polarity, because of its simplicity, but, in practice, the use of resistance 
thus inserted and removed, for the purpose mentioned, has not been very successful 
in quadruplexy. A more successful method is shown in Fig. 161, in which t rep- 



FIG. 161. 




■>!!!!i^|i|ili!i^/ 



resents a transmitter; pc a pole-changer and nr and pr (as in Fig. 160), a Morse, or 
Stearns relay, and polarized relay, respectively. 

In this arrangement the decrease of current is obtained by cutting off a large 
portion of a battery b, when the transmitter is open, as in the figure, and the in- 
crease of current is obtained by employing the entire battery, which it may be seen 
is done when the transmitter is closed. The connections of the system are so ar- 
ranged that whether a portion only of the battery, or the full battery, be placed in 
circuit by the transmitter, that portion, or the full battery, will be reversed by the 
pole changer. For example, when the transmitter t is open, as in Fig. 161, it is 
seen that only that portion of the battery between i and 2 is in use and the n da- 
tive pole of the smaller portion is to the line, the pole-changer being closed. 



THE QUADRUPLEX. 



197 



It is seen that whether the transmitter be open or closed there will be an avail- 
itDle battery to the line. The object in so arranging the connections of the trans- 
mitter that, whether open or closed, there will be available battery at the terminal 
of the circuit, is to insure the working of the polar duplex feature of the system, 
since it is clear that, as it depends for its operation upon the reversals of polarity of a 
battery, or other source of electromotive force, there must be provided, in either position 
of the transmitter, a source of electromotive force to reverse. If then the relay nr 
be adjusted, as stated in connection with Fig. 160, so that, when the smaller portion 
of the battery is placed to the line its armature will be withdrawn by the , retractile 
spring, we can see that, in Fig. 161, the relay ne will be '' open," and the position of 
the armature of the polar relay will depend on the direction of the current in its 
coils, etc. 

In Fig. 162, the key, or transmitter, t, is closed; consequently, the wire leading 
from 2 in battery b to the left hand contact point of t, is open, and the full battery is 

Fie-. 162. 




■HwWr/ 



placed to the line. The result is that the armature of nr is attracted. As, how- 
ever, the pole-changer has not been opened, the polarized relay has not been affect- 
ed. It will be observed, however, that should the pole-changer be operated now, it 
will reverse the enfi're battery. 

The relays kr and pr are supposed to be at the distant end of the line ; pc and 
T being at the home station. Thus, as in the case of Fig. 160, the polarized re- 
lay will repeat only the signals transmitted by the pole-changer, and the Stearns relay 
those due to the variations in the strength of the current produced by the operation of 
the transmitter. 

The electro-magnets of PC and t, the sounders and local circuits of nr and pr 
have been omitted to avoid complicating Figs. 160, 161 and 162. 

In practice the smaller portion of the battery is termed the " short end;" the point 
at which the wire divides the battery, is termed the "tap ;" the wire so tapping it the 
"tap wire;" the larger portion of the baj^tery the "long end." In the Quadruplex, 
the Stearns, or Morse relay, is generally termed the "neutral" relay. 



198 AMERICAN TELEGRAPHY. 

Operation of the quadeuplex. — It may be doubted whether in the whole 
range of applied electricity there occur more beautiful combinations, so quickly 
made, broken up, and others reformed, as in the operation of the quadruplex. For 
example, it is quite demonstrable that during the making of a dash on the neu- 
tral relay at one station the distant pole-changer may reverse its battery several 
times; the home pole-changer may do likewise and the home transmitter may in- 
crease and decrease the electromotive force of the home battery, repeatedly. At the 
same time, and, of course, as a result of the foregoing actions, the home neutral 
relay may have had its magnetism reversed several times, and the signal will have 
been made, partly by the home battery, partly by the distant and home batteries 
combined; partly with current on the main line, partly without; partly by the 
main line " static ' ' current, and partly by the condenser current, and yet on a well 
adjusted circuit it will have been heard on the quadruplex sounder as clearly as any 
dash on an ordinary "city line" sounder. 

A theoretical diagram of the duplex, as arranged in ]iractice, for the gravity bat- 
tery " key system," with connections and apparatus at botli ends, x and y, is given in 
Fig. 163, and by its aid a descripticn of the manner of operation of the system, and of 
some of the combinations just referred to, will be attempted. 

PC, Pc' are pole-changers, t and t' are transmitters, mb, mb' are main batteries, 
divided as shown, nr 8nd nr' are neutral relays, the main and artificial line coils 
of which have each a resistance of about 200 ohms. Rs, rs' are '■ repeating" soun- 
ders, the function of which will be stated, s', s, s, s' are the "reading, or regular soun- 
ders. PR and pr' are polarized relays, each of whose coils has a resistance of 400 
ohms. r,r' are rheostats of the artificial lines, c, c' are condensers which compen- 
sate for the static induction of the main line. cr and cr' are resistances to retard the 
currents to and from the condensers. 



In the figure, PC andT, at station x, are shown closed, while, atT, they are open. 
Assuming the battery to be divided into two parts, as shown, and that the smaller 
part is one-fourth of the whole battery, the ratio of current from the small end 
as compared with the full battery will be as i to 4. The arrows indicate the 
direction of the current through the several coils of the relays. The figure under each 
coil may, for the purpose of illustration, be supposed to indicate the strength of cur- 
rent in the coils under the assumed existing conditions. For instance, in the left 
hand coil of nr and pr the strength is 5; in the right hand coils the strength is 4; 
while the strength of current in the left coil of pr' and nr' is i, and in the right 
hand coils, 5. 

Since these currents are flowing through the respective coils of the relays in op- 
posite directions it is plain that the current available for producing the magnetic effect 
on the cores of those relays, nr and pr, is the excess of 5 over 4, namely i ; and in 
the cases of pis' and nr' the resulting. magnetic efi^ect is due to the excess of 5 over i, 
namely, 4. 

That such is the case may be ascertained by consideration of the following: The 
full battery mb at x is placed to the line. We assume that it givefe a current strength 



200 AMERICAN TELEGRAPHY. 

of 4 to the right hand coils of nk' and pr', at y. The transmitter t' at y being open 
the small portion of the battery mb' is placed to the line; the "long" end of that 
battery being open. Thus a strength of but i passes to the artificial line r' from 
mb' and a similar current strength is Mded to the main line coils, making the strength 
in the main line coils of all of the rekys, 5. 

For convenience hereafter in this description the excess of current in one coil 
over the other may be termed "excess" current. 

It will be premised that the springs of the neutral relays are so adjusted that 
when the excess current in one coil over the other is represented by i, the armature 
will be withdrawn from the front stop, but that when the excess is represented by 4 
the increased magnetism will overcome the pull of the springs and the armatures will 
be attracted. 

Now, at X, the excess current in the line wire coil of nr is i, consequently, the 
armature is withdrawn and its sounder s, is open. But, at y, the " excess '' in the line 
wire coil of nr' is 4 and the armature is attracted and the sounder s' is closed. This 
should be expected since the transmitter at X is closed and the transmitter at y is 
open. In both cases the polarized relay is irresponsive, the only effect, which is not 
a visible one, being that the armature will be attracted to its cores more or less 
strongly, as the case may be. 

If now the transmitter t, at x, be opened, it will be found that only the short end 
of MB is in service, its long end being open. The result is that now a current strength 
of but I flows in the artificial coils of nr and pr, and a strength of 2 in the main line coils 
of NR and PR and nr' and pr'. This is plainly so since the current of i from battery 
mb' is added to that of mb in the main line coils. The excess of current, therefore, in 
the coils of the relays is now but, i and, hence, the armature of nr' is withdrawn ; 
both neutral relays now being open. And it will also be found, on extimination, that 
regardless of what poles of the batteries may be placed to the line the home neutral 
relays will be closed when the distant transmitter is closed and open when it is 
open. Of this an example will be given. 

Let PC andx, at x, remain as in Fig. 163 and let pc' and t', at y, be closed. This 
places the negative pole of the full battery at each station to the line. We shoulc! 
now find that this change closes the neutral relay nr at x, and reverses the position 
of the armature of pr, which is the case, as we shall see. A result of the changes 
referred to is that no current flows through any of the main line coils, inasmuch as 
the potential at each terminal of the main line is now equal and similar, but a cur- 
rent strength of 4 now flows in each artificial line coil. Thus the neutral relay at 
X is closed and the neutral relay at y, which had been closed by the excess cur- 
rent of 4 in the main line coil, remains closed. Before the closing of the pole- 
changer at y we saw that pr at x was magnetized by an excess current of i in 
the main line coil flowing in the direction indicated by the arrows. Fig. 163^ It 
is now magnetized by an excess current of 4 flowing in the opposite direction around 
its core and, consequently, the magnetism of its core is reversed and its armature 
is moved over against its contact point, closing, thereby, its sounder. 

As regards the effect of the closing of the pole-changer and transmitter at 
Y, upon the relays nr' pr', it will be found to be nil; for those relays had already 



THE QUADRUPLEX. 



20I 



been magnetized by a current strength of 4, which had been flowing in their main 
line coils in a certain direction around their cores, which direction was similar 
to that of the excess current of 4 now flowing in their artificial line coils. 

It is again suggested to the student desirous of following out the foregoing that he 
draw for himself diagrams to meet the changed positions of the apparatus and direc- 
tion of the current. [Further allusion to the actions just referred to as well as other 
analogous actions occurring in the operation of the quadruplex will be found in con- 
nection with description of diagram, Fig. 166.] 



Polarity of elected- magnets due to dieection of cuerent aeound coees. 



It may further aid the student to a comprehension of the electro-magnetic actions 
touched upon in the foregoing to understand what the polarity of a given end of an 
electro-magnet will be with a current around its cores in a given direction. 

For example, referring to 
F^G. 164. Fig. 164. If one is looking 

at a given end of a core, a 
current in the coil around 
the core from right to left 
*will make that end of the 
core a south pole, a and b, 
Fig. 164. If the current is 
flowing in the coil around 
tlie core from left to right, as 
in c, the end looked at will 
be a north pole. 

It will be noticed that the 
winding of b is the reverse 
of that of A, and, although 
the direction of the current 
through the wires a and 
B is opposite, still, owing to 
the difference in the winding 
of the coils, the direction of the current around the core is the same in each case and, 
hence, the poles of the cores are the same. 

Moment of no magnetism in neuteal relay.— In quadruplex telegraphy, as 
already mentioned, the differentially wound Morse relay is termed the "neutral" relav 
because of its practical neutrality to reversals of polarity of the current. 

Since, however, the neutral relay nr, is in the same circuit, and subject to the 
same influences as the polarized relay pe, it is clear that whatever changes of mao-net- 
ism take place in the polarized relay must also occur in the neutral relay. In otlier 
words, every reversal of the battery which reversesthemagneticpolarity of the i>olanzed 
relay must also reverse the magnetic polarity of the neutral relay. 

* That is, as the hands of a clock move around the dial, as on7is lookiiv^^^aUt" 





202 AMERICAN TELEGRAPHY. 

Between each reversal of magnetisin, there is an interval when there is no magnet- 
ism in the core of the relays. At this moment of " no magnetism" the armature of 
the polarized relay simply retains its last position. When the armature of the 
neutral relay is on its back stop, it is immaterial whether the magnetism of the core 
be reversed or not. When, however, that armature is on its front stop, being held 
there by the full distant battery, against the pull of its retractible spring, it will, at 
the moment of " no magnetism," recede from the front stop. But the recession is only 
momentary, as, almost instantly, the relay is again magnetized, and attracts its arma- 
ture. If, however, the local circuit of the sounder be connected to the front stop of the 
neutral relay nk, there is, at the moment of no magnetism, opportunity for that circuit 
to open, when the armature momentarily flies back, and thus produces a false signal, 
or "kick," in the local, or reading sounder s. This was found to be the case in practice 
and to overcome this defect, one of the first things done by Mr. Edison was to place the 
local circuit contact of the neutral relay on the back stop, as shown in Fig. 163, so 
that the effect of the reversal of the distant full battery upon the local sounders of 
that relay might be reduced to a minimum ; for it is plain that the duration of contact 
of the armature lever of nr upon its back stop, will be but a fraction of the total time 
that it is away from its front stop during the moment of " no magnetism." 

As this arrangement of the contacts would deliver the signals on the *' back " 
stroke, a "repeating" sounder RS, Fig. 163, with local contacts on the up stroke, is 
used to convert the signals received on the reading sounder s, to the front 
stroke. The interpolation of the repeating sounder between the relay and reading 
sounder still further tends to prevent the false signals on that sounder, since the re- 
peating sounder must first be fully magnetized before it will withdraw its armature 
from the upper contact. 

■ It may be added that the use of the repeating sounders is not now imperatively 
necessary, and, in many instances, it is dispensed with, the connections of the quadru- 
plex transmitter being transposed so that tlie '' short " end of the battery is placed 
to line when the transmitter is closed, and the "full" battery, when it is open. 

On very long lines the effect of the "kick" due to the reversal of the entire dis- 
tant battery is much increased; in other words, the reversal of the magnestism of the 
relay is more gi-adual, and, consequently, a longer duration upon its back contact is 
allowed its armature. 

To further diminish the period of no magnetism in the neutral relays, the contact 
points of the pole-changer are adjusted as closely as practicable and the neutral relay 
is, as a rule, constructed of the best soft iron, with very short cores, to facilitate mag- 
netic reversals. 

"While, as intimated, the detrimental effect due to the recession of the armature 
of the neutral relay, at the moment: of the distant reversal is, in many instances, prac- 
tically, eliminated by placing the contact on the back stroke, it is known that the 
efficiency of the quadruplex system would be increased if the moment of no magnetism 
in the relay could be further diminished, or, so to speak, tided over. 

To accomplish this result a number of ingenious devices have been brought out, 
some of which will be herein described. 



203 




204 AMERICAN TELEGRAPHY. 

Smith condenser akrangement. — One of these, namely, ttie Smith condenser 
arrangement for diminishing the period of no magnetism in the neutral relay, is shown 
theoretically ia Fig. 165, in connection with the other quadruplex apparatus at one 
station ; namely, PC the pole-changer, t the transmitter, nk and pk the neutral and 
polarized relays, and R, CR, cc, the rheostat, etc., of the artificial line. 

In the Smith condenser arrangement, which has been extensively employed on the 
quadruplex circuits of the Western Union Telegraph Company, the neutral relay nr is 
furnished with a third coil, 3, as shown. This coil is in the circuit of a condenser sc, 
whose terminals are connected, respectively, to the main and artificial lines. eg kg' 
are resistance coils of about 600 ohms each, the object in using Avhich is to obtain a 
difference of potential between the plates of the condenser when the distant battery 
is to the line, in a manner to be ex'plained. 

When the distant end of the line is " grounded," and when the balance between 
the main and artificial line is secured, no difference of potential will exist at the termi- 
nals of the condenser, and, consequently, it will not be charged. When the distant 
battery is to the line, a difference of potential is set up between the plates of the con- 
denser, and a charge is accumulated which will be discharged at the moment of reversal 
of the distant battery. And it will be found, on investigation, that the current of 
discharge, which then flows in the third coil of the relay, is in an opposite direction to 
that of the " excess " current which had previously been circulating in the main or arti- 
ficial line coils of the relay. The result is that the reversal of the magnetism of the 
relay is accomplished very rapidly ; even before the effect of the actual reversal of the 
distant battery may be felt in the home relays. In this way the time of '• no magnet- 
ism" in the relay is reduced and the tendency to a false signal diminished. 

By the aid of diagram Fig. 166, the various changes of potential produced in the 
plates of the condenser by the reversals of the distant battery may be graphically 
illustrated. (For some explanatory remarks concerning diagrams of this kind the 
reader may refer to Chapter VIII. See Wheatstone bridge.) 

In Fig. 166. The horizontal line al, ml, represents the resistance of the artificial 
and main line circuits, respectively, each having a resistance of 3000 ohms from 
the junction at J, which may correspond to the junction of the main and artificial 
wires of the quadrUplex at the home station. 

In what follows the letters al and ml will stand for artificial line and main line, 
respectively. 

The vertical line v represents the e. m. e. of the home battery at x, with the 
full battery of 300 volts, positive j^ole, to the lines, al and ml. This vertical line is 
subdivided into sections 10, 20, etc., indicating the e. m. e., at those points. Simi- 
larly, the distant battery at y is represented by vertical line v' ; the portion of that 
line below ml representing the full battery with negative pole to line ; the portion 
above ml representing the full battery with positive pole to line. 

The horizontal line z may represent the potential along the main line when positive 
poles at X and t are to the line ; at which time, assuming a thoroughly insulated 
Ime -wire, there is no fall of potential along the wire. The inclined line w 
may represent the fall of potential on the wire when the negative pole of the full 



206 AMERICAN TELEGRAPHY. 

distant battery is to line; the line s, the fall of potential on the artificial line al, re- 
gardless, practically, of the polarity or e. m. f. of the distant battery. The dotted 
line D indicates fall of potential on main line from x when the distant end is to 
ground, direct; the line e the fall when the small end, positive pole, of distant 
battery is to the line. 

The resistance of 3000 oJims is supposed to include the resistance coils, kc, of 
Fig. 165, the relay coils at the home and distant stations, and the internal re- 
sistance of the distant battery. 

In the Smith condenser arrangement the terminals of the condenser are placed 
between the main and artificial wires, behind the 600 ohm coils. In Fig. 166 the 
terminals of c, are shown connected to al and ml, at points 600 ohms removed from j. 
The wavy lines rc correspond to the 600 ohms resistance coils. The "turns," at nk, 
nr', PR, pk' represent the main and artificial line coils of the home relays; eg the 
third coil of the neutral relay. 

As the changes to be shown by this figure will be due to reversals of the distant 
battery only, it will be assumed that the '' home '' battery will remain constantly, at 300 
volts positive potential, and, for the sj^me reason, the artificial line at the distant end may 
be neglected. 

Assuming, first, that the positive pole, 300 +> of the entire distant battery at Y 
is to the line, the horizontal line z from y to x indicates the potential on the main li.j,«; 
that is, there is then no fall of potential along the wire. There is, however, a fal' of 
pressure along the artificial line, as indicated by the line s. 

At this time then, the main line terminal of the condenser is at 300 -|- volts poten^ 
tial as indicated by the point at which the vertical line ^ intersects the line z; and 
the AL terminal of c is at 240 -|- volts potential as indicated by the point at which the 
vertical line a' intersects the line s. Consequently, the condenser c will receive its 
charge, which will be due to a diiference of potential of 60 volts at its terminals, 
from the point of higher j^otential, namely, the main line terminal; in the act of re- 
ceiving which charge a momentary current will be set up in the third coil, around the 
core of the neutral relay in a direction assisting in the magnetizing of the core. This 
being so, it is evident that the discharge current of the condenser, which is always in 
the opposite direction to that of the current of charge, will pass through the third 
coil in a direction tending to reverse the previously existing magnetism of the relay, 
in which case it will curtail the moment of ''no magnetism" in the relay, since, 
by tending to reverse the magnetism of the relay the condenser, by its discharge, 
does what is desired to be done by the ensuing reversal of the distant battery. 

When the entire distant battery is reversed, thereby, in the case assumed, put- 
ting the negative pole to line, the line w will represent the fall of potential along 
the main line. In this case it is seen that the ml terminal of the condenser is at 
180 volts potential, as indicated by the point at which the vertical line b 
intersects the line w, while the al terminal remains, as before, at 240 volts — still leaving 
a difference of potential of 60 volts between the plates. The condenser now, however, 
receives its charge from the al terminal and its charging current is opposite in di- 
rection to that of the previous charging current. Therefore, its next discharge cur- 
rent will be in the opposite direction to that of the previous " discharge " current. 



THE QUADRUPLEX. 207 

And it will be found that the discharge currents of the condenser will always be in 
a direction, at the moment of " no magnetism," to deprive the relay of its previous- 
ly existing magnetism, while the currents of charge will assist in magnetizing it to 
a polarity coinciding with that due to the ensuing reversal of the distant battery. 

The effect of a reversal of the distant battery at the time the short end of bat- 
tery is to the line has not thus far been considered. Inasmuch as the armature of the 
home neutral relay is on the back stop at that time, it is evident the distant re- 
Tersals will not have any effect upon the armature. The charge and discharge of 
the condenser, of course, proceed as usual, but with much reduced effect. This will 
be seen by further reference to Fig. 166. 

Assuming the short end of distant battery to be 100 ^ volts, the fall of potential will 
he as indicated by line t, which shows that the ml terminal of the condenser is now at say 
220 volts potential, while the al terminal is at 240 volts as before. But, now, there is 
only a difference of potential of 20 volts between the plates of the condenser, and 
since the magnitude of its current of charge and discharge depends primarily upon the 
difference of potential between its plates, it is plain that the current in the latter case 
will be much diminished. Nevertheless, tliis diminished current must be felt in the 
relay, and on fine working "margins" should tend somewhat to reduce the value of 
the device, since the pull on the spring of the relay must be increased, be it ever so 
little, to counteract the magnetic pull of the core due to the charge of the condenser 
when the short end of distant battery is to the line. 

It may be asked what the effect upon the Smith condenser would be of reversing 
the home battery ? Practically none. The reader may prove this to be the case by 
turning Fig. 166 upside down, and changing the -\- and — signs to meet any hypoth- 
etical conditions of the batteries required. 

It has frequently been noticed in practice during stormy weather — also at other 
times — that the margin is increased on the neutral relay, by *' short-circuiting " the 
condenser of the Smith arrangement. This is probably due, chiefly, to the fact that 
the third coil of the relay is now free to be acted upon by the *' regular" currents of 
the system, set up by the action of the distant transmitter. It will be seen by reference 
. to Fig. 165 or 166 that the third coil is, practically, in the bridge wire of a Wheatstone 
bridge, when the condenser is cut out, and that the relay itself is in a combination of 
the differential and bridge methods for preventing the effect of the home battery upon 
the home relays. 

The Frier Self-Polarizing Neutral Relay. — This relay has been found to give 
the most satisfactory results in the Western Union service of any relay yet de^-ised 
for the second side of the quadruplex, to the extent that it has become the standard 
form of neutral relay employed in that service. In this as in other forms of neutral 
relays there is, of course, a moment of no magnetism, but the results of its operation 
show that it is not so marked as in some other forms, which is most likely due to the 
form of construction whereby the self-induction of the instrument is lessened, the 
cores, as will be seen, not being connected by a yoke or cross-piece, and also to the 
lightness of the moving parts, whereby its responsiveness to weak currents is in- 
creased, and in consequence of all of which its " figure of merit " is increased. By 



20^a AMERICAN TELEGRAPHY. 

figure of merit is meant the reciprocal of the least amount of current necessary to 
operate the relay efficientl3\ For instance, if the necessary current should be .014 
ampere the figure of merit would be ,-:^ = 701. Obviously the lower the current 
strength required the higher the figure of merit. 

Another term used in connection with the operation of circuits and relays is 
" time constant," which is the time required for the current or the magnetism to reach 
a certain fractional part of its maximum strength, namely, the ^Vu¥ of that value'^ 
The time constant is equal to the self-induction of the circuit or relay divided by 
its resitetance. The henry is the unit of self-induction and it is defined as "the induc- 
tion in a circuit when the electromotive force induced in this circuit is one volt while 
the inducing current varies at the rate of one ampere per second." For example, 

Fig. iZoa. 




if a relay on short-circuit has a current of i ampere flowing through its coil and if 
the lines of force set up by this current fall from maximum to zero in i second and 
in doing so set up an electromotive force of i volt, the self-induction of the relay 
is I heury. 

Referring to the time constant, if the self-induction of a relay be, say, 4 henrys, 

and its resistance be 300 ohms, its time constant is ■^=J-^ of a second. If the self 

xi-aiction and capacity of a circuit or relay were nil the current or magnetism woukL 

attain its maximum strength immediately. {See Self-induction, also Healy Xeatral 

Eelav, page 230; also foot-note, page 318, and Appendix.) 

In form and external appearance the Frier relay is almost identical with the 
polarized relay shown in Fig. 154, but with the permanent magnet removed and aTi 
electro-magnet put in its place. The manner of its operation is practically as fol- 
lows: Its armatures are pivoted adjacent to the pole-pieces of the extra electro-mag- 
net M, Fig. i8o«, and they vibrate between the pole pieces of the electro-magnets 

* This subject is treated from this standpoint more fully, theoretically, in Fleming's "Alternate Current Transformer."' 
page 103, Vol. I. Another definition of "time constant ""' is that it is the time the current takes to rise from zero to its 
maximum and to fall as:ain to zero. Preece and Stiibbs state that the highest speed in telegraphy requires that the time 
constant of the hue shall not exceed l-23Utii of a second. This is p:esama1jly at the rate of 450 words per minute. 



THE QUADRUPLEX. 20/^ 

E e'. In Fig. iSoa the relay is shown in a side view and the description will for sim- 
plicity only consider the armatures and pole-faces as there shown. 

The electro-magnet m, like e e', is differentially wound and its coils are inserted 
in the main and artificial lines of the quadruplex circuit, in series with the respective 
coils of the electro-magnets e e'. A magnetizing current in the coils of m will, of 
course, magnetize its coi^e, the result being that one of its ends will be a north, the 
other' a south pole, and these poles in turn will, by induction, magnetize the arma- 
tures in proximity thereto, practically as if the pole-pieces of m were permanent mag- 
nets. If, wdth ii given magnetiziog current through m, the end of the core shown in 
the figure be a north pole, the end of the armature between the pole pieces e e' will 
also be anorth pole, and since the connections of the coils of e e' are such as to en- 
sure that the pole pit ce of the regular electro-magnets which are opposite each other 
will be of opposite polarities, the north pole of m will be attracted to that pole-piece 
which the same current has made a south pole, and repelled from that pole-piece 
which has been mpde a north pole. {See pages 303, 304, Wheatstone relay ) 

In the figure the south pole is shown at e, and consequently the armature is at- 
tracted to that side. If now the direction of the magnetizing current be reversed in 
the coils, that end of the armature between the pole-pieces e e' will become a south 
pole, while the pole-piece of e will become a north pole and that of e' will become a 
south pole, the total result being that the armature is still attracted to pole-piece e. 
Hence it is evident that, regardless of the reversals of the distant battery, the arma- 
ture will continue to be attracted to pole-piece e. Since the armature lever of the re- 
lay is provided with a retractile spring, as in the case of the neutral relays already 
described, it will be obvious that it may be adjusted like the armature of that relay, 
in such manner that it will only be attracted towards the pole-piece e' when the CLtire 
distant battery is to the line. 

It has been found that the best adjustment of this relay is obtained when the 
armatures are close to the attracting pole of the electro-magnets and at some distance 
from the repelling pole. This is especially the case in fine w^eather, but is not so 
noticeable in bad weather when the magnetizing current in the coils is diminished. 



Ratio of current strength with transmitter closed as against trans- 
mitter OPEN. — We have seen that the polar duplex feature oi the quach'uplex re- 
quires that a certain amount of electromotive force should be on the wire when the 
transmitter is open. The amount of this e. m. f. is regulated by the minimum 
strength of current found necessary to properly operate the polarized relays. The 
maximum e. m. f is regulated by the amount of current required to properly operate 
the neutral relays. This is generally in the ratio of 3 to i or 4 to i with key closed 
as against key open. 

With a battery of 300 gravity cells the ratio of 3 to i would be secured by put- 
ting the tap wire at 100 cells ; the ratio of 4 to i by placing it at 75 colls. 



C08 AMERICAN TELEGRAPHY. 

We may also utilize Fig. i66, or its equivalent, to graphically follow all of 
the changes that occur in the relays in the actual working of the quadruplex, among 
others, those by which, for instance, the operation of the transmitter effects, the 
changes in the current strength flowing in the coils of the neutral relay. It is only 
necessary to remember that the current flowing in the coil, or coils, of a relay, as in any 
other conductor, is due to the difference of ]^otential between its terminals, and 
that the magnetizing current of the differential relays is due to the "excess" of 
potential difference between the terminals of one coil, over that between the termi- 
nals of the other. 

For example, take the case of the neutral relay. Fig. i66. First, supposing the 
distant station to have its full positive battery to the line. It is seen, by tracing 
the vertical lines a /j to line z, that the terminals of the main line coils of that re- 
lay are at equal potentials, hence no current flows in that coil. By lines s s it is 
seen that the a' terminal of the al coil of nr' is at 240 volts and the ^' terminal at 
220 volts; thus the current in the al coil, which in this case is the magnetizing current 
of the core, is due to a potential difference of 20 volts. The strength of this current 
will be found by Ohm's law, namel}' the quotient of the e. m. f., or difference of 
potentials between the terminals of the coil, divided by the resistance of the coil — in 
this case = ^^^^y, that is -^^ ampere. 

Now, assuming thenegativebattery to be to the line at distant station t, the fall 
of potential is shown by line w, and the ^ terminal of the ml coil of nr is at 180 
volts while the a terminal of the same coil is at 140 volts, a potential difference be- 
tween the terminals of 40 volts. The current in that coil is, therefore, due to that 
potential difference. The terminals of the al coil of nr' remain as before, namely, 
with a potential difference of 20 volts between them. Consequently, twice the current 
flows in the ml coil at this time that does in the al coil, but, as the currents flow 
in opposite directions, around the core, the " excess " magnetizing current is only 
what would be due to a potential difference at the terminals of either one of the coils 
of 20 volts. That current is, of course, in the opposite direction to the "excess" 
current which had existed in the al coil before the distant reversal. 

If now it is assumed that the short end and negative pole of the distant battery 
be put to line — and that it has an e. m. r. of 65 volts — the fall of potential on the 
main line will be represented by the line t'. In that case the j^otential at the ^ ter- 
minal of nr will be 225 volts; that of the rt! terminal at 200 volts, a difference of 
25 volts at the terminals. The potential difference at the al terminals of nr' still re- 
mains as before, namely 20 volts, consequently, the " excess" current in the ml coil is 
due to a difference of 5 volts ; that is one-fourth of what it was with full distant 
battery; thus showing that tlie ratio of current strength, as between transmitter 
closed and open, is as 4 to i, which Ave know would be the case with the tap at 75 
volts in a battery of 300 A^olts. 

The resistance of the coils of the polarized relay being double that of those of 
the neutral relay, the potential difference between the terminals of its respective 
coils will be double that at the respective terminals of the neutral relay coils, but as 
the resistance of the polarized relay coils is twice tha.t of the neutral lelay coils tlie 
current that flows in the respective coils of both relays will always be the same. 



THE QUADRUPLEX. 209 

That would follow from the well-known law that the strength of current is the same 
in all parts of an undivided circuit. The added convolutions of wire, other things 
being equal, would, of course, produce a greater magnetizing effect in the core with 
the same current strength. 

The effect upon the home relays of placing the small end of the distant positive 
battery to the line when the full battery is to the line at the home station, may be 
Studied by the reader, if desired, by aid of line e. Fig. 166. 

ACTION OF THE CONDENSER AS A STATIC COMPENSATOR. 

Even an outline description of the various combinations set up in the relays by 
the operation of the pole-changers and transmitters would be incomplete without a 
reference to the very pretty automatic action of the condenser as a *' static compen- 
sator." 

Unless the writer is mistaken this action is not generally understood. The text 
books, hand-books, and patent specifications which he has seen have generally united 
in describing the action of the condenser in its capacity of static compensator, in 
duplex telegra])by, when it is employed to give to the artificial line a static capacity 
equal to that of the main line, practically as follows: — 

" The return current from the line," (as the static d scharge of the line was for- 
merly called,) "passes through one coil of wire of the electro-magnet, with the same 
fttrength and at the same time, but in a reverse direction to that of the return cur- 
rent from the condenser passing through the other coil of the wire. Thus the effects 
of induction are neutralized. " 

The impression conveyed, and in some instances distinctly stated, is that, at 
the moment the above described action is taking place, the electro-magnet, or relay, is 
without magnetism, and, consequently, the false signal due to the static discharge, or 
return current, is obviated. 

The present writer thinks it can be shown that the only time when the forego- 
ing explanation is strictly accurate is in the Stearns duplex when the distant end is 
to " ground," and the distant battery is, consequently, cut off. It can also be shown, 
in duplex telegraphy, with the condenser in the artificial line, that the line return 
current sometimes assists in producing the signals and that sometimes the condenser 
"return current" assists in producing them, and that, in the polar duplex and the 
quadruplex, it rarely, if ever, happens that the action of the condenser as a static 
compensator conforms to the action as stated in the quoted explanation. 

The present writer's attention was first called to the insufficiency of the forego- 
ing explanation by a consideration of this fact, namely, that it does not explain 
what it is that, in the quadruplex, retains the home neutral relay against its front 
stop, when the entire distant battery is to the line, at the time that the home trans- 
mitter, or home pole-changer, especially the latter, is being operated. 

If the effect of the static induction be neutralized as indicated in the state- 
ment quoted, the armature should, at the instant of " neutralization," fly away from 
its front stop, but it does not do so. Some other explanation is, therefore, necessary; 
the following one Avill, it is thought, meet all the requirements. 



2IO 



AMERICAN TELGRAPH-Y. 



Fig. 167 may represent a portion of a Stearns duplex system. The main line 
wire ML is shown as having the ground nearly adjoining it throughout its length. 
It may also be considered that the artificial line consists of a senes of condenser 
plates along the length of the rheostat Rh, as in the manner of tlie " Muirhead " 
artificial cable. (See Submarine Telegraphy.) 

With the positive pole at x and the negative pole at y, to the line, the excess cur- 
rent in ML coils of relay nr will be in the direction indicated by the arrows, and the 
core will be magnetized and its armature attracted by the current in that coil. 

Without going minutely into the actual distribution of the static charge along 
the main line and artificial line, it will be sufficient, for tlie present purpose, 
and will simplify the explanation, to assume that the main line and the condenser 
have at x a static capacity rendering them capable of acquiring, under the given 
conditions, a potential of loo -{- or — volts. 



FIG. 167. 



Jt^^ 



.THi 






J00 + 



e^I, 




100- 



/lA 



!N"ow when the key at x is opened and the wire is thereby placed to the ground, 
as in Fig. 168, the currents of static discharge should be due to 100 volts positive po- 
tential, and as, at the moment of discharge, the main and artificial lines are at a high- 
er potential than the earth, the current from both of those lines, if nothing opposed 
the action, should be towards x, and, in that event, as one current would op]30se 
the other in the coils of the relay, demagnetizing it, the armature of nr would 
fall back at an inopportune time and make a false signal. 

As, however, this false signal does not appear on a well balanced line, it is evident 
that something, other than a simultaneous discharge of the condenser and the line, occurs 
at that moment; and this we may see is the case. 

If the currents of static discharge from both the main and artificial line come 
towards x, the presence of the assumed 100 + volts, due to the static induction 
of the line, is evidently the equivalent of placing, momentarily^ 100 volts of negative 
polarity in or to the main line and artificial line at x. Consequently, as the regular 



THE QUADRUPLEX. 



211 



battery of lOo volts negative polarity is already ' on * the main line at y, the result is 
a momei]tary cancellation, as it were, of all current on the main line, and, therefore, 
there is, for the time being, no current in the main line coil of the home relay ne. But, 
at that same instant, the condenser discharge takes place through the artificial line 
coil of the relay, and as its direction around the core of nr, (j^^ arrows, Fig. i68). 
corresponds to the direction of the previous magnetizing current, {see ml coil, Fig. 167), 
the magnetism of the relay is maintained without interruption. 

Fig. 168 is supposed to represent the conditions at the moment of putting the 
line to earth at x. 

The action of the condenser may be considered practically instantaneous; before its 
current of discharge ceases to affect the relay, or simultaneously with such cessation, the 
line static discharge, which had been, as it were, holding back the distant battery current, 
also dies out, and the current from the distant end assumes control of the relay, its 



FIG. 168. 



.ysrji 



■>rlOO- jviL 




100- 



Y 



INSTANT OF STATIC DISCHARGE. 



direction being such, again, that it flows in the main line coil in the same direction around 
the core as the current from the condenser had just been circulathig. If it should seem 
to the reader that the act of cancelling, or nullifying, the current on the main line at the 
moment stated would tend to open the distant relay, it may be remarked that this 
would simply assist in accomplishing the object of opening the key at x, which object 
is, at that time, to open the distant neutral relay. 

In the foregoing instance we see that the signal from the distant station is partly 
made by the condenser at the home station. 

If now, for further illustration, the battery at y be reversed, placing the 100 volts 
positive pole, to the line, but retaining the 100 volts, i)ositive, to the line at x, as in Fio-. 
169, there will then be no current on the main line, but the relay at x will be mao-- 



212 



AMERICAN TELEGRAPHY. 



netized and held towards its core by the current from the battery at x through the 
AL coil. 

When the key at x is again opened, putting the line to earth, we may see that the 
effect of the static discharge at x will be, as before, virtually, to place a battery of 
negative polarity of loo volts to the line at x. But as now a battery of loo + polar- 
ity is to the line at y, tlie effect will be, at the moment of static discharge, to moment- 
arily double the current in tlie main line coil of the relay. The condenser, as before? 
also discharges, as shown by tlie arrow, but its current is overcome by the " excess" 
current in the main line coil; and as this excess current is in the same direction around 
the core, as that of the magnetizing current which has jnst been liowing in the al coil, 
the magnetism of the relay is not affected. 

In this latter case we have the signal from the distant station made partly by the 



FIG. 169. 



JVB + 100 - 



,ML 






C-WMWWW. 



|l 



li u I 
2 



-i»o -f| 



JiL 



ioo+ 



C tHh 



combination of the line static discharge and the distant battery ; the effect of the 
condenser discharge being nullified. 

Wiiile, for simplicity, the Stearns duplex has been chosen for the purpose of illus- 
tration, it will be found, on examination, that the foregoing will suffice to explain any 
of the conditions due to static charge and discharge occuring on the polar duplex or 
the quadru])lex. 

The foregoing may be amplified by means of Figs. 169^, 169^, showing the as- 
sumed effects of the line and condenser static effects upon the relay in the "bridge^' 
wire when the " bridge ^^ duplex is employed. 

In these figures ml and al may represent the main artificial line of, foi the sake 
of simplicity of description, a Stearns duplex, each line having 3000 ohms resistance. 
V and y' will represent the home battery of 300 volts, positive and negative respect- 
ively ; E and e' the positive and negative distant electromotive force ; a a' the 



THE QUx\DRUrLEX, 



212^ 



Fig. i6ga. 



resistances of the arms of the bridge, say 600 ohms each. The relay in the bridge 
wire is represented by R. 

In Fig. i6ga it is first assumed that the home battery has 300 volts positive 
polarity to the line, and that the distant battery of 300 volts negative polarity is to 
the line. In that cas3 the sloping dotted line s will represent' the fall of potential 
along the main line, while dotted line z' may represent the fall along the artificial 
line. In that case the potential at the z' terminal of relay r will be 240+ volts 
and at the s terminal 180+ volts, as indicated by the vertical dotted lines b b'. The 
direction of the current in R will, therefore, be from the point of higher to the 
point of lower potential, or from left to right, as indicated by the arrows. 

In the explanation of this theory it is assumed, for simplicity also, that at the 
moment when the home battery is removed and the Hue is placed to ground, the 

currents of static discharge from 
the line and condenser are due 
to an electromotive force prac- 
tically equal to that of the home 
battery, but of opposite polarity, 
it being known that the current 
of static discharge is in the 
opposite direction to that of 
charge. 

Let the solid lines in Fig. 
169^5, then, represent conditions 
^^" at the moment of static dis- 
charge at the home station. Then, the distant battery remaining unchanged, 
the electromotive forces of static discharge may be supposed to bring about 
momentarily the conditions represented by the horizontal line F and the sloping 
line f', in which case the artificial line terminal of the relay will yet be at the point 
of higher potential (240 negative being higher than 300 negative), and the current 
will continue to flow in the same direction through R, as shown by the arrows. 

If now, as in Fig. 169^, it be assumed that the distant battery has been reversed, 
as, for example, in the polar 
duplex, putting the positive pole 
to the line, the positive battery 
at A being to the line as before, 
the charge or potential on the 
main and artificial lines may 
be represented by the dotted 
lines zz'. In this case, the line 
terminal of the relay is at the 
point of higher potential, the 
result being that the current 
now flows through the relay 
from right to left, as should be expected from a reversal of the distant batterjo 

When now the line is next put to ground at A, the electromotive forces of static 




300- 





Fig. i69<5. 
^00+ 


^ 2_„. 


300+ 


.^:" 


Z40 
200 

too 
A 


X ^ 




V 






■.jy 


/ 


ML 


V. 


R 








/F 



212(5 * AMERICAN TELEGRAPHY. 

discharge may be indicated by the solid sloping lines f and r\ Fig. 169^*, in which 
case the main-line terminal of li is at the higher 23oint of potential, and a current still 
flows from right to left in that relay. Hence the combined effects of the distant 
battery and the static discharge of the main and artificial lines evidently is to main- 
tain the magnetism of the relay at the same polarity as that dne to the action of the 
distant battery, thereby preventing false signals in the home instruments at the mo- 
ment of static discharge at the home station. 

The 8TUMM Added Eesistance ok Duplex and Quadkuplex Ciecuits.— 
This consists of placing a certain amount of resistance in the mainline in wet weather, 
for the purpose of improving the working of the second side of the quadruplex. The 
author's theory of the admitted beneficial action of this device, as given to the U. S. 
Patent Ofiice on behalf of the inventor, Mr. F. A.Stumm,New York, is that it dimin^ 
ishes the effect of rapid variations of the main line insulation resistance upon the 
" balance " of the relays. In other words, the imperfect working of the neutral side 
of the quadruplex is not due so much to an insufficiency of working current, as to 
the rapid variations in the main line insulation resistance which upset the line 
'^balance/' For example, it is obvious that if by placing, say, 900 ohms in the 
main line (which must be compensated by 900 ohms in the artificial line), thus in- 
creasing the apparent resistance of the line from 900 ohms to 1800 ohms, a variation 
of, say, 225 ohms in the mainline will then act on the "balance" only in the ratio 
of 225 to 1800, as against the ratio of 225 to 900 without the added resistance. 

It is sometimes stated that the merit of this device lies in preventing the line 
resistance from falling so low as to interfere with the proper operation of the resist- 
ances in the Field key system. Analysis, however, shows that this view is erroneous. 
Thus, assume a normal line resistance ml of 1800 ohms, and that wet weather has 
apparently reduced this resistance to 900 ohms. This presupposes a line escape 
(call it ML^) equal to 1800 ohms. Assume also an e.m.f. of 225 volts and a ratio of 
3 to I in current strength with key closed as against key open. Then with key 
closed joint resistance of al (artificial line) and ml, ml^ is 450 ohms, which with 600 
ohms at dynamo (see Fig. 176) gives a total of 1050 ohms. The resulting current 
at J is 225 -^ 1 050 = . 214 ampere, of which al takes .107 ampere, ml takes .0535 
ampere, and ml' takes .0535 ampere. With key open the total resistance is 600 -f- 
1200 -|- joint resistance from J of L, al, ml, ml' (300 ohms) = 2100 ohms. Now 
225 -^ 2100 = .107 ampere, of which al takes .0359, ml takes .0179, ^^l' takes 
.0179, and leak takes .0359 ampere. Thus the proportion of current to line with 
key closed and open is respectively .0535 and .0179, or 3 to i. With the Stumm 
added resistance of, say, 900 ohms in circuit, the artificial line balances against 1800 
ohms, and analysis will show that now, with key closed, the total current at J will 
be .15 ampere, of which al takes .075, ml takes .0375, and ml' takes .0375 ampere. 
W^ith key open the current at J will be .1 ampere, of which l takes .05 ampere, al 
takes .0250 ampere, ml takes .0125, and ml' takes .0125 ampere. Thus with key 
closed the current to line is .0375, as against .0125 ampere with key open; that is, a 
ratio of 3 to I in current strength. Hence in each case, with and without Stumm 
resistance, the proportion of current to main line is 3 to i with key closed and open 
respectively. 

TEEMIJ^TAL COI^NECTIOI^S. W. U. QUADRUPLEX. 

In Fig. 170 are shown the terminal connections of the Western Union Quad- 
ruplex when operated with gravity battery. 

The local connections are shown by the letters ?Z; t is a transmitter; PC the 
w. u. pole-changer; nr the 3-coil neutral relay; PR is the polarized relay ; sc are the 



214 



AMERICAN TELEGRAPHY. 



"Smith " condenser; cc are the boxes containing the 600 ohm coils; SP is the 3- 
point switch for putting line to ground at the desk; sc is the "spark-coil" with 
resistance equal to internal resistance of long end of the battery; se is the short end, 
le the long end of the main battery, ck is a "combination " rheostat, so called because, 



FIG. 171. 



5^^Coii: 




WESTERN UNION NEUTRAL RELAY. 



within its covers, are contained several separate series of resistance coils; rr and c^' 
represent the retarding coils placed before the static compensating condensers c^ c^ ; 




r is the resistance coil equalling the resistance of the main line; gc is the ground coil, 
thrown into circuit when the switch sp is turned to the right in the figure ; its resistance 
is made to equal the internal resistance of the full battery mb. 



THE QUADRUPLEX. 



215 



FIG. 173. 




REPEATING SOUNDER. 



The connections, as shown in Fig. 170, are, of course, apt to be transposed, in 
some respects, in practice, but they may be easily verified by following out the actual 
desk connections. It is always 
well in practice not to rely 
too implicitly on any dia- 
gram of such connections until 
they have been verified. 

The three-coil neutral relay is 
shown as it appears in prac- 
tice in Fig, 171. The combin- 
ation rheostat in Fig. 172, and 
the quadruplex repeating sound- 
er in Fig. 173. 

The three-coil neutral 

eelat — winding of. 

The manner of winding the 
three-coil relay is shown theo- 
retically in Fig 174; only a 
few turns of each coil being shown, for the sake of clearness. 

A and B represent the " bobbins" of the relay. The bobbins are made of hard 
rubber, the cylinder or tube into which the iron core of the relay fits, being made very 

thin. This serves as an additional sate-guard 
to prevent the wire short-circuiting with 
the core. The rubber tube is not shown in 
the figure, e e e e are the ends of the 
bobbin. The ends of the core c, c. cp is the 
iron cross-piece connecting the two cores. 
Three coils of wire, i, 2 and 3, are wound 
on each bobbin. The first coil consists of 
about 1800 turns of wire. A sheet of tissue 
paper is placed over this coil. Then 
a second coil of 1800 turns is wound over 
the first; another sheet of tissue paper is 
then placed over the second coil, and a third 
coil of 1800 convolutions over that. 

The wire used is about No. ^6, B. W. 
G., silk insulation. 

As it is very difiicult to draw wire of 
this diameter which will have a uniform 
resistance throughout its length, the man- 
ner now to be described of connecting the 
coils on the bobbins has been adopted. 

The coil i on a is connected to coil 

2 on b; coil 2 on A to coil i on b. As these 

WINDING 3-coiL NEUTRAL RELAY. ai'c til c " differential '' coils, it is very esseii- 




2 1 6 



AMERICAN TELEGRAPHY. 



tial tliat they sliould "be of equal resistance, and have an equal magnetic effect 
upon the cores when an equal current is passing around each. This arrangement of 
the coils effects this desideratum in a high degree, hv distributing the resistance of the 
two coils over the two bobbins. 

Coil 3 on A is connected to coil 3 on b. 

The resistance of the coils i 
and 2 varies from 200 to 22:; 

FIG. 175. . ■-' 

ohms. That of the third coil 
is nearly 400 ohms, which is 
due, of course, to its greater 
length, it being the outside coil 
on each bobbin. 

Smith arraxgemext of cox- 
densees foe ecoxomizixg 
SPACE. — Especially in large 
offices the available room un- 
der the desks is frequently 
much diminished, to the dis- 
comfort of the operators, by the 
number of condensers, " leak " 
boxes, etc., employed in quad- 
ruplex telegraphy. In order 
to improve this condition, Mr. 
Gerritt Smith devised the ar- 
rangement shown in Fig. 175, 
by means of which the removal 
of the duplex or quadruplex 
condensers to a less crowded 
quarter is made feasible, without 
in the least detracting from 
the ease with which the instru- 
ments may be adjusted. This 
device consists of a duplicate of the " adjusting " end of condensers, diminished in size, 
mounted on a suitable base-board b, and placed conveniently upon the desk. The 
crescent-shaped and numbered discs, on the base-board b are connected by insulated 
wires to correspondingly numbered discs, on the ends of the condensers, as shown, 
which latter, as previously intimated, miiy be in a separate room. The strips s s on B, 
are connected to the artificial line through the resistances r, r\ the strips on the 
condensers c, c', to the earth. Thus the act of plugging or unplugging a disc on the 
base-board is equivalent to plugging or unplugging similar discs at the condenser. 




SMITH ARRAXGEMEXT OF CONDENSERS TO ECONOMIZE SPACE 



DYNAMO KEY SYSTEMS. 71 7 



Dynamo-Ouadruplex Key Systems. 

Owing to the difficulty that presented itself in the attempt to operate any sys- 
tem of telegraphy, requiring reversals of polarity, from dynamo machines which were 
also required to furnish,at the sam3 tLme,current, of a stated polarity, to other cir- 
cuits, it was necessary, if duplex and quadruplex circuits were to be supplied with 
current developed by such machines, that means should be devised to reverse the 
polarity on the circuits, without reversing the machines in the sense that a gravity 
battery is reversed in duplex and quadruplex telegraphy. It was also necessary that 
means should be provided to increase and decrease the strength of current on the quad- 
ruplex circuits. 

The difficulty in utilizing reversals from dyna^ no machines when employed as 
stated, consists in the fact that if a dynamo be reversed for one circuit it will re- 
verse the direction of current in all the other circuits that may be connected to it. 
This would, of course, be equally true if an attempt should be made to reverse, for 
one circuit, a gravity or other battery to which other circuits may be connected. 

It was, comparatively, an easy matter to secure reversals of polarity by using a 
pole-changer, which, in one position, was connected with a series of dynamo machines 
furnishing positive polarity and, in the other position, to another series of machines 
furnishing negative polarity. 

To secure the necessary increase and decrease of current for the quadruplex sys- 
tem, without changing the existing forms of transmitting apparatus, was not so 
easy of accomplishment. It was, of course, known that increased and decreased 
strength of current could be obtained by '' cutting " resistance coils in and out of 
the circuit, but experience had shown that this method of securing the variation in 
current strength was not very successful ; the resulting action of the relays ueing 
more or less sluggish. 

To obtain a quick acting "increase and decrease" of current on the quadruplex 
circuits for the operation of the distant relays, without affecting the resistance of the 
main line and without changing the construction of the existing apparatus was the 
object in devising the dynamo quadruplex key system, (due to Mr. S. D. Field)^ 
which is in use in all the cities where the Western Union Telegraph Company ha& 
replaced gravity batteries by dynamo machines. 

Western Union or Field Dynamo key System. 

This key system successfully provides an increased and decreased streno-th of 
current in the distant relays without any change in the previously existing trans- 
mitter, and with, in fact, a simplification of the pole-changer. 

In the Field key system the desired ratio of current strength is secured by 
varying certain resistances in the main line and in a short branch circuit to earth; 
the combination of which, as will be shown, effects the desired result without, auy 
actual increase in the resistance of the main line circuit. 



2l8 



AMERICAN TELEGRAPHY. 



176. 

1Z00 R 

msimsmmsiSLr 



■^22Jv 




ty^L, 




900 



J>' 



1SOO 






fSOO 



In the gravity battery key system, as has been shown, the decrease of current 
is secured by reducing the electromotive force at the sending end of the wire and 
this is effected by cutting out, by means of the transmitter, any desired number of 
ceils. 

In the Field dynamo key system the same result is accomplished, namely, the 
placing of the sending end of the wire at a lower potential, (but without cutting 
out, or off, any portion of the source of electromotive force,) by means of the combi- 
nation of the added resistance and branch circuit to earth, just alluded to, which 
combination is under control of the transmitter. 

In the operation of this 
key system the laws of "joint 
resistance " and of " divided 
circuits" are largely con- 
cerned; the reader, if not 

^ ^ , . familiar with those laws, is 

^^ I ^ therefore referred to Chapter 

It , on Dynamo Machines in 

which those laws are discus- 
sed. (Chap. III). 

The theory of the Field 
key system is outlined in 
Figs. 176, 177 and 178. 

Fig. 176 is a theoretic dia- 
gram of the key system 
at one station with main and 
artificial lines only shown. 
In this figure d, d are dynamo machines each supplying 225 volts, r ?-' are re- 
sistances of 600 ohms placed between the dynamos and pole-changer pc to lessen 
the intensity of the spark at 
the contact points, etc. e is 
an "added" resistance of 
1 200 ohms. When the trans- 
mitter, '1, is closed, as in 
Fig. 176, this resistance is 
short-circuited by the short 
wires i and 2, via the post 
p and tongue is' of the trans- 
mitter. L is a resistance of 
900 ohms, termed the "leak," 
between the lever of the 
transmitter and earth. 
When the transmitter is 
closed, L is open at the bend 
B of the transmitter lever. 
Thus when t is closed, both k and l are virtually out of the main circuit and, so far 



FIG. 177. 

rzoo R 




FIELD KEY SYSTEM. 



219 



FIG. 178. 



iSoo It 

smsimmsmir 



as those resistances are concerned, the full strength of the current goes to the main 
and artificial lines. When t is open, however, r is put into the circuit and l is tapped 
on to the circuit, at j, via wire 2, as may be seen in Fig. 177. 

The object of this device is to cause, at the distant station, a variation in the 
strength of current equal to what would be caused by cutting off two-thirds of the 
cells of a gravity battery; that is, to produce a ratio of 3 to i in the current, as be- 
tween the key closed and open. This we shall see it does. 

In Figs. 176, 177, 1 78 the 
main and artificial lines are 
supposed to have a resistance 
of 1800 ohms each. The joint 
resistance of those circuits 
from J would then be 900 
ohms. 

In Fig. 176 the only other 
resistance in the circuit is 
the 600 ohms, r', at the 
minus pole of dynamo ma- 
chine d'; hence the total res- 
istance of this circuit, with 
T closed, will be 600 -[- 900 
= 1500 ohms. This gives 
a current strength in the 
At J the current divides equally 




vML. 



§ fSOO 



circuit, up to j, of .15 ampere (/. e. -yHq = .15). 
between al and ml, each wire taking .075 amperes. 

Counting from j to the ground, via r' and the dynamo d', it is seen that the 
resistance is 600 ohm?. 

Referring now to Fig. 177, in which t is open, we find that the resistance of 
the circuit from d' to j is 600 + 1200 = 1800 ohms. The joint resistance of al, 
ML and L, from j, is 450 ohms. The total resistance of this circuit is, therefore, 600 
+ 1200 -\- 450 = 2250 ohms. This gives a strength of current up to j of 2W0" — -^ 
ampere. This current is now divided between al, ml and l in inverse proportion to 
the resistances of the branch circuits. As the joint resistance of al and ml is 900 
ohms and the resistance of l is also 900 ohms it is clear that the current will divide 
equally between al and ml, and l. Hence l will receive J of .1, that is, .05 and 
AL and ml will each receive :[ of .1, that is, .025 ampere. 

Or, this may be arrived at in another way. The total resistance of this circuit, Fig. 
177, from dynamo d' is, as said, 2250 ohms. Between d' and j the resistance 
is 1800 ohms. Consequently, as the fall of potential is proportional to the resistance 
*' overcome," the potential will have fallen, at j, iff ^ of 225 volts, namely, 180 volts. 
Hence the potential at j will be 225 — 180 = 45 volts. Thus the strength 
of current flowing in al will be, by Ohm's law, ijf — -^-S J^i^P^i'^j ^^^^ iii ^l 



the same; while, in the branch l it will be ^-f-^ = .05 ampere. We saw that 
with T closed, ML and AL each received .075 ampere. It is evident then, from the 



2 20 AMERICAX TELEGRAPHY. 

foregoing, that the ratio of i to 3, as between t open and closed, is thus secured on the 
main line .075 : since thrice .025 is .075. 

Further, reckoning also from j to the ground, via the two routes, namely, the 
leak Tl 900 ohms; and the dynamo (ir'oo -f- 600 ohms = 1800 ohms) we find 
the joint resistance to be 600 ohms. Thus, while the desired reduced strength of 
current has been effected on the main line and at the distant end, by the insertion 
of the resistances, etc., at the home station, the resistance from j to the earth at the 
hom.e station has not been altered so far as regards the distant station. 

At times, in practice, it is desired to increase the ratio of current strength, as, for 
instance, to make the ratio 4 to i. In the Field key system tliis result is brought 
about by making the added resistance 1800 ohms and the "leak'' l, 800 ohms. 
This change is outlined in Fig. 178. 

With the transmitter closed it has been shown that the added resistance is not in 
cii'cuit, and that the " leak '■ is cutoff. Hence the current strength to line will be 
the same with transmitter closed in Fig. 178 as in Fig. 177, the e. m. f., at the dyn- 
amo machine not having been altered, With the transmitter open, however, it is 
different, and it will be found (by a calculation similar to that made in the case 
of Fig. 178 of the varying joint and total resistances which exist under the con- 
ditions brought about hy opening and closing the transmitter. Fig. 1 78,) that the 
variation in the current strength with key closed, as compared with it open, is now 
as 4 to I. This result will be graphically illustrated in Fig. 179. 

In practice when this ratio is increased the total electromotive force is also 
generally increased. 

It has been noted that the total resistance presented to the distant station is 
not, in the Field key system, altered, in either position of the home transmitter, 
owing to the fact that, in either case, the total, or the joint resistance, from the point 
J to .the earth at the home station is 600 ohms. But the resistance from j to 
the ground at the dynamo d', in say. Fig. 176, is, with transmitter closed, 600 ohms, as 
against 1800 ohms, with that instrument open. And it is this change in the resistance 
in combination with the short route to earth via the leak, which, by lowering the 
potential at j, is chiefly instrumental in bringing about the aforesaid variation in the 
current strength at the distant station. 

This effect will also be found graphically illustrated in Fig. 179; as will also the 
manner in which the variations of electromotive force at the home station affect the 
current strength in the distant neutral relay. 

For the sake of simplicity the distant battery at t is not included in the fig- 
ure, it having already been shown, in the cases of the polar duplex and the "gravity" 
battery quadruplex key systems, that the presence of the distant battery in the circuit 
does not affect the result intended by the operation of the " home " transmitter or 
pole-changer, upon the distant relays. But any reader may construct for himself 
diagrams showing the varied conditions that will occur in the operation of this key- 
system. It will be found an interesting study. 

In Fig. 1 7 9, let X represent a home station and y a distant station. The ver- 
tical lines Di, D2, Dg, the electromotive force, under the varying conditions of the 



THE QUADRUPLEX. 22 1 

key system at x. The horizontal line ml, may represent the resistance of the main 
line from x to t, with the transmitter closed at x 

The resistance of the main line from the junction j of the main and artificial 
lines at x, to the ground at y, is assumed to be 1800 ohms, as in the case of Figs. 
176, 177, and 178. The resistance of the artificial line from j to ground will, of 
course, also be 1800 ohms. The resistance from the dynamo d' at x, to y, which in- 
cludes the 600 ohms at the dynamo machine, is 2400 ohms, as marked, and this re- 
sistance is represented by the thick line ml. The thick horizontal line ml, ar, will 
represent the resistance from d' to Y with the transmitter at x open, yi\\Q\\ the key 
system is arranged for a ratio of i to 3, in which case the added resistance of 1200 
ohms is placed in the circuit. The line ml, ak, ar' will represent the resistance 
from d' at x to Y,v/hen the key system is arranged for a ratio of i to 4. The elec- 
tromotive force at xis assumed to be 225 volts, negative polarity. 

As already stated the electric pressure at any point of the main line, may be 
ascertained by drawing a vertical line from ml to any of the sloping lines, and by 
drawing, from the intersection of those lines, a horizontal line to the vertical lines rep- 
resenting the E. M. F. For instance, in Fig. 1 79, the vertical line «, drawn from ml 
to the line tc', shows the pressure on the main line, 1600 ohms from d', to be 60 volts. 

With transmitter <r/^i-<?^ at x,(ratio 3 to I ) the total resistance presented to the 
dynamo at x would be 1500 ohms from d'; that is, 600 ohms at the machine, plus 
the joint resistance of the main and artificial lines from j, namely 900 ohms. 

If this resistance were contained in a single wire from d' to ground the fall of 
^pressure could be represented by the line tc, kt. It may then be considered for il- 
lustration purposes, that the fall of pressure from d' to j is the same as if the circuit 
were composed of a single wire measuring 1500 ohms from i>' to ground, and, hence, 
the pressure at J may be found by drawing a line w from vertical line j' and kt 
to the line d' — it is found t3 be 135 volts. 

From the junction j, the fall to '• ground," via the different wires, (main and arti- 
ficial wires) is proportional to the resistance of each wire. The resistance of the 
main and artificial lines in this case being 1800 from j to the ground, the slope, or 
fall of potential may be represented by sloping line tc'. 

As the main line to station y is joined at j to the wire leading to the dynamo 
machine at x, the line tc' which indicates the fall of pressure along the main line, 
ML from J to Y, joins the lines tc and kt at w^ in the figure. 

The 200 ohms resistance of the main line coil of the' neutral relay at y is in- 
dicated by NR. This coil will be utilized to show the decreased current due to 
opening of the transmitter at x. 

With transmitter at x closed it is seen that the coil of nr has, at its terminals 
a potential difference of 15 volts, which is indicated by lines a b n ;/', the a 
terminal being at 60 volts, the b terminal at 45 volts. The current flowing in nr 
will, of course, be due to this potential difference divided by the resistance of 
the coil, namely, 2W ampere. 

With the transmitter at X open (ratio 3 to i) the resistance of the circuit from 
the dynamo at x is increased, by the added resistance, 1200 ohms, which, as it were, 
places the macliine back to ar. 



222 AMERICAN TELEGRAPHY. 

The fall of pressure at j, reckoned from ar, is now due to the dynamo resist- 
ance of 600 ohms and the added resistance of 1,200 ohms ar to d^ plus the joint re- 
sistance of the main and artificial lines and the leak of 900 ohms {See Fig. 177), 
which gives a total resistance of 2250 ohms. 

The fall along a single circuit of that resistance would be indicated by the line 
KG, from line d^. Hence, the potential at j, at this time, as shown by the intersecting 
line n from j, kg, is but one-third of what it was with the transmitter closed at x, 



FIG. 179, 




22^- 



225- 



THE FIELD KEY SYSTEM (THEORY.) 



namely 45 volts, and the line kg' now represents fall of pressure along main line ml; 
that is, with transmitter open at x. 

Hence, the potential difference at the terminals of ml coil of ne is, as indicated 
by the lines a b and r /, 5 volts; the potential at a terminal being 20 volts, that dXb 
terminal, 15 volts. Consequently, the current now flowing in that coil is equal to the 
E. M. r. of 5 volts, divided by the resistance 200, that is you ampere, which is, 
obviously, one-third of ^% ampere, which was the current strength in coil with 
transmitter at x closed. 

When the ratio of 4 to i is desired, the 1,800 ohms added resistance is inserted 
and the "leak" is changed to 800 ohms. In this case, when the transmitter is 
open, the dynamo is virtually placed at ar' as in the figure. 



THE QUADRUPLEX. 223 

The total resistance then offered to the dynamo from ar' at x would be 2825 
ohms. The fall of pressure along a single wire having a resistance of 2825 ohms 
from D3 at ar' is shown by the line to. 

As the 2)oint of joining the main and artificial lines to the wire leading to the 
dynamo has not been changed this places the junction j at a point where the pres- 
sure, or potential, is 33.75 volts, that is, one-fourth cf what it was with transmitter 
closed, as may be seen by reference to horizontal line m drawn from intersection of 
vertical line j and sloping line to to vertical line D3. 

The slope of potential along the main line, ml, from j, with transmitter open, is 
now indicated by slope to', and it may be seen by the lines t c that the potential 
difference at the terminals of nr is now but 3^, or 3.75 volts, the pressure at terminal 
a l)eing 15 volts, that at b \\\ volts. Consequently, the current now in the coil nr 
^^ I'Jt ampere, which is one-fourth of -^^^ amperes; the latter being the current 
strength in coil with key closed at x. Or, as in a previous case, the foregoing results 
may be proved in another way. Thus, for instance, since, with the transmitter at x 
closed, the potential at the junction j of the main and artificial wires is 135 
volts, and as the resistance of ml is 1800 ohms, it is evident that, at the a terminal 
of XR, the potential will have fallen "through" \%%% of the total resistance of ml; and, 
as, in doing so, the pressure will have fallen \%%% of 135 volts it evidently has 
dropped 75 volts at that point, making the pressure at terminal a, 60 volts, as in the 
diagram. (The a terminal being 1000 ohms from j.) 

Thus, it is again seen that the same result is obtained by the opening and closing 
of the transmitter in this key sytem as is obtained by decreasing and increasing the 
number of cells, which is the office of the transmitter in the gravity battely key sys- 
tem; the function of the " added" resistance and the " leak" being, as intimated, to re- 
duce the pressure at the junction j. 



TERMINAL CONNECTIONS WESTERN UNION QUADRUPLEX. 

In Fig. 1 80 is shown the terminal connections of the present standard quadruplex 
system and apparatus of the Western Union Telegraph Company. It will be seen 
that the Field key system is still employed, but that the Smith condenser arrange- 
ment has been dispensed with ; the Frier self-polarizing relay taking its place. The 
oblong form of rheostat has also given way to the Varley rheostat v r with radial 
arms, the general principle of which is fully described in connection with the Wheat- 
stone automatic system, page 317. The form of polarized relay pr shown in Fig. 154 
iaalso used in place of the Phelps relay, and a somewhat new form of transmitter t 
in which the supports and lever are of tubular brass is now employed. The local con- 
nections are shown by the letters II. p c is the dynamo pole-changer. The leak box 
L B is shown with the arrangements for varying the ratio from i to 3 to i to 4 or vice 
versa, as desired. The ratio is varied by cutting out or putting in the 600 ohm coil 
of the added resistance and the 100 ohm coil of the leak, which is done by inserting 



224 



AMERICAN TELEGRAPHY. 



FIG. l8o. 




TERMINAL CONNECTIONS WESTERN UNION QUADRUPLEX. 



J^IE QUADRUPLEX. 225 

pin plugs between the discs on the end of ihe box, or by removing them. In the fig- 
ure a plug is inserted cutting out 600 ohms of the added resistance. No plug is in- 
serted in the leak, hence the box is arranged for the ratio of 3 to i. The cut-out 
switch c s, consists of three 3 point switches or arms on one base-board. Arm i when 
to thn right opens the circuit leading to dynamo d. Arm 3, turned to the right opens 
circuit to d'. Arm 2 when turned to the right grounds the line wires through resist- 
ance in vr'. The Field pole-changer consists of a brass lever l supported on the 
usual beariugs. p and p' are brass posts having contact points on their upper end. 
The lever is also equipped with contact points opposite these posts. The post p is 
connected to one dynamo machine via the cut-out switch c s. The post p' to another 
machine of opposite polarity. The line wire is connected to the lever of the pole- 
changer via the cut-out switch. Thus when the lever of p c is operated it presents to 
the line a different polarity at each change of position. This form of pole changer 
was devised to diminish sparking at the contact points, this having been found a ser- 
ious defect in the old style of pole changer when used in connection with high poten- 
tial dynamos. The artificial line is connected to an arm s on v r, which arm accord- 
ing to its position on certain posts inserts or cuts out resistance coils of 3,000 and 
6,0c o ohms, respectively, in addition to the coils connected with the radial arms, prac- 
tically on the principle of pin p Fig. 237. The box v r' contains the resistance inserted 
before the static compensating condensers c', c", r r are the resistances placed in 
each circuit as described in Chap. TTI. 

A condenser is now in many instances placed between the lever l of PC and the 
ground to reduce the spark at contact points. Mr. S. D. Field tested this device in 
1882, but it was not found of utility, rather the reverse. -Perhaps condensers of too 
high capacity were then employed. A condenser of about .5 m. f. is now found to 
be of decided advantage. The condenser is adjusted until the best results are ob- 
tained. Apparently the spark occurs at the making of contact, and it has therefore 
been thought that the sparking was due to the static discharge jumping to the lower 
contact point before the making of contact, but this does not seem likely in view of the 
high E. M. F. necessary to rupture cold air, say 4,000 volts for -^-^ inch. Several 
theories might be advanced to explain the action of the ^' spark" condenser in this 
capacity. For example : In this form of pole changer there is evidently a rebound or 
a series of rebounds of the lever at the making of contact, and it is probably at th.e 
breaking of circuit during these rebounds that the spark tends to occur. If, for 
instance, the positive dynamo machine. Fig. 159, has been placed to line, the spark 
condenser and the line would both have a plus charge. Then when the lever L 
started to reverse polarity it would first open at p. Any tendency of the positive 
current of D to follow the lever would then be opposed by the positive charge in the 
condenser ; it being assumed that the static dis&harge from the line might be held bark 
momentarily by the opposing e. m. f. of the relays. When the contact is made at \\ 
one or several actions may follow. The spark condenser and line may discharge in 
multiple through the negative machine, and immediately take a negative charge. 
Whereupon if the break due to a rebound of the lever now occurs, the negative charge 
in the spark condenser will oppose the tendency of the negative current to follow the 
contact point at the reliound. Or the sparking may be reduced by the charge of 
the spark condenser holding back the line discharge while the lever is in transit be- 
tween contact points, etc. 



226 AMERICAN TELEGRA^\iY. 



The Postal Telegraph Company's Quadruplex. 

The theory of the quadruplex system used by the Postal Telegraph Company, 
with the dynamo as the source of electromotive force, is shown in Fig. 182 * In the 
operation of this system the " increase and decrease ' of current principle, in combina- 
tion witli that of reversal of polarity, is utilized. 

When, in this system, gravity battery is employed the quadruplex key system 
already shown is used. When dynamo machines f re availed of the ratio of current 
strength, as between transmitter open and closed, is obtained by transposing the cir- 
cuits from one dynamo machine of, say, 225 volts to one of, say, 
75 volts or vice versa — and the reversals of polarity are secured by transposing the 
circuit from a machine of, say, positive, to one of negative polarity. 

The manner in which this is done will be plain by reference to Fig. 182, in 
which PC, Pc' act as the pole-changing instruments. They are, for clearness, shown 
as having separate electro-magnets, but it is evident the contact points could be 
supported on one lever, thereby dispensing with one of the electro-magnets. 

As the electro-magnets of PC, pc', are in the same local circuit botli will open 
and close together when the key k is operated. The contact point i of pc is con- 
nected by wire to a " negative " machine of 225 volts; contact point 2 with a "posi- 
tive" machine of 225 volts. Contact point i of pc' is similarly connected to a neg- 
ative machine of 75 volts ; contact point 2 to a positive machine of 75 volts. Tlie 
lever /, of pc is connected by a wire to post / of t ; lever /', of pc', to lever l^ of t. 
The tongue x^ of t, is joined to a wire leading to tlie main and artificial lines, r, r, 
r, r, are the usual resistances inserted between dynamo machines and the office ap- 
paratus to diminish sparking. The operation of this key system may be described as 
follows : 

When transmitter t and pc and pc' are closed the circuit from the earth passes 
via the 225 -f- volt machine to the lever /of pc, thence via post ^ of t to the line 
wire. When T and p(, pc' are open the circuit will be from the earth via the 75- 
volt machine to /' of pc' and via the lever Poi t, to the line. Or, again, for example, 
if T should be closed and pc, pc', open, the circuit will be from the earth via the 225 
volts negative machine to the line. Thus, at every opening or closing of the trans- 
mitter T, the electromotive force, and consequently the current strength, is decreased 
or increased^ and at every opening or closing of the pole-changer pc, pc', the current is 
reversed ; the strength of current "transmitted" from the home station depending on 
the position of t, regardless of the position of pc and pc', and the jDolarity, or 
direction, of that current depending on the position of pc, pc', regardless of the posi- 
tion of T. , 

The receiving instruments of this system are shown to the right of transmitter t. 

NR is a neutral relay having three electro-magnets. Its electro-magnets e, e' are 
"differentially" wound and their coils are in the main and artificial lines, as shown. 
EM is a "singly" wound magnet which is in the circuit of the secondary wire of au 

* This arrangement of the quadruplex, due to Mr. F. W. Jones, is being displaced by the Field-key system {see Fig. 
176). Instead of the usual pole-changer and transmitter with horizontal levers, 16-ohm relays with vertical levers are 
employed, as outlined in Fig. 182a. pc and t (opposite pagt^. The inductorium ic and extra coil em are also being re- 
placed with a modification, due to C. E. Diehl, Fig. 1826, of the Edison repeating sounder device (page 202). In Fig. 
182&, NR is the Jones neutral relay, coil eM of which is idle. Contact x of a 20-ohm relay rs is on front stop. When 
lever of nr is on back contact c, current from the 40- volt dynamo is shunted from coil of ks to earth by way of wire a a 



-^OTBOcmreu^ 



227 




and 200-olmi resistance, at which times relay rs and consequently sounder s are open. "When the lever of xr is on its 
front stop, shunt circuit a a is open at c, and curient passes through coil of rs, nuignetizing it. and attracting its arm- 
ature, closing circuit of s at x, whereupon s is magnetized. It will be seen that by this arrangement the magnetism of 
RS not only has to be brought to full strength (which consumes time) before its armature a' is attracted, but also that 
armature must travel from the back to the front stop before the reading sounder s will be at all alTeeted, thus miui- 
mizing the opportunity for false signals at the moment of no magnetism iu nu. c' is a cut-out switch. 



2 28 AMERICAN TELEGRAPHY. 

induction coil ic. ic is a differentially wound induction coil having two primary 
wires, one of which is in the main line circuit, the other in the artificial line circuit. 
Consequently, the core of ic is only affected when an excess of current exists in 
either one of those coils, and a current is only induced in the secondary coil at the 
moment w'neu the excess current is set up, or is subsiding, as when the distant battery 
is being reversed. 

The lever a, carrying the armatures a a\ is pivoted at o; thus the cores of the 
different magnets, when magnetized, all tend to move the lever in tlie one direction. 
The object of the use of the two main and artificial line magnets e and e' is to 
obtain an increased effect upon the armature lever, thereby to secure a better work- 
ing margin. 

The extension, Ex, from the lever a, carries. the armature a"^ of the extra magnet 
EM. At the reversal of the distant battery there is, of course, the usual reversal of 
magnetic polarity in the " home " relays. At that time an extra current is set up in 
the secondary wire of the induction coil, ic, and, as the extra magnet, em, is in the cir- 
cuit of the secondary wire, the core of em is momentarily magnetized and attracts its 
armature, thereby tending to hold the armature lever, a, against its front stop dur- 
ing the moment of no magnetism in the cores of the magnets e, e'. In other re- 
spects the action of this neutral relay is practically similar to the ordinary quadru- 
plex neutral relay. 

PR is the ordinary polarized relay, e is the "artificial" line rheostat, c is the 
static compensating condenser and ^r is the resistance for retarding its currents of 
charge and discharge. 



"New York" Quotation Company's Quadruplex. 

This quadruplex also employs in its operation the "increase and decrease" of 
strength principle, in combination with reversals of polarity. 

The reversals of polarity are obtained in the usual way, namely by transposing the 
line from a machine of one polarity to a machine of opposite polarity, by the use 
of a pole-changing instrument. 

The decrease of strength is secured by 'tapping ' ' certain resistances, placed be- 
tween the dynamo machines and the ground, at a point where the potential will 
be such as to give a desired ratio in the strength of current as between transmitter 
open and closed, and, at the same time, to keep the total resistance of the line wire 
a t a uniform value whether the transmitter be open or closed. 

The manner in which this is done is indicated in Fig. 183, which also shows ia 
outline the form of pole-changer and neutral relay employed in this system, which is 
due to Mr. C. L. Healy. 



230 AMERICAN TELEGRAPHY^ 

The resistances pe, pr', are permanently connected, as shown, between the ground 
and dynamos d, d'. t is a ''double" transmitter, the magnets of which, being in the 
one local circuit, are jointly affected by the key k. When k is closed the full current 
stuength is to the line. The upper contacts c, c', of the transmitter t' are led to a 
point in the permanent resistances pr, pr' where the potential has fallen to a desired 
degree. 

For instance, if the total resistance of pr, pr', be 1200 ohms, each, and it is 
desired to obtain the ratio of current strength of 3 to i, and the electromotive 
force of each machine is,say, 225 volts, the "taps" p, p' would be placed at a point 
400 ohms from the ground, where the potential will have fallen to 75 volts. 
Thus, when the transmitter, t, is open, auE. m. f. of but 75 volts is offered to the line, 
while, when the transmitter is closed, the full e. m. f. is virtually placed to the line. 

It is obvious that the total resistance from, say, the contact c to the earth, via 
the tap P, would be the joint resistance of a and b, from the tap p; that is, the joint 

resistance of 800 ohms and 400 ohms, which is — = 266 ohms. Tliis re- 

800 + 400 

sistance may be considered as the equivalent of the internal resistance of a gravity 
battery. Therefore, to insure that the resistance from the junction J of the main 
and artificial wires to the earth at ..he home station shall be the same in either posi- 
tion of the double transmitter t, resistance, such as br, br^ equal to the joint resist- 
ances of « and <^, is placed between contact points ex, or ex', and the dynamo ma- 
chines D and d'j respectively, which resistance (br br') in this case, would be 266 ohms. 
The pole-changer pc consists of an electro-magnet whose armature is carried by 
a stiff, upright lever l, which plays between two contact points x^ x' . When the 
pole-changer is closed, current is taken from the positive machine, d, via c or ex. 
When the pole-changer is open, current is drawn from the negative machine d' 
via c' or ex' 

The Healy neutral relay, nr in the figure, is of peculiar construction. 
It has two separate cores which are differentially wound. The cores are com- 
posed of small iron wires bundled together and insulated from each other. This 
arrangement of the cores is to facilitate reversals of the magnetic polarity. The relay 
has two armatures which are carried on a brass shaft s, passing between the cores. 
The shaft is pivoted on the bearings f, f '. The ends of the cores are cut slantingly, 
and the armatures, which are made of very light iron, are twisted into a form re- 
sembling the blade of a propeller, so that each end of an armature may face, evenly, 
the slanting end of a core. Thus the magnetic circuit of the cores is completed 
through the armatures. One of the armatures carries an extension, the upper end of 
which plays between tAvo stops, one of which has a contact point, in the same way as 
does the lever of the ordinary relay, excepting, however, that, owing to the pecu- 
liar construction of the armatures, the lever moves at right angles to the length of 
the cores, instead of to and from them. 

In the regular form of quadruplex neutral relay the entire length of core, in- 
cluding the cross-piece, is about 4 inches. This leaves about two inches on which 
to wind the coils. The cores of the Healy neutral relay furnish 2\ inches space on 
each core on which the coils may be wound, and, also, a shorter length of iron to reverse 



"NEW YORK QUOTATION COMPANY S QUADRUPLEX. 23I 

at the time of distant reversals, it being assumed that the cores of each coil will 
demagnetize simultaneously. 

The polarized relay, pr, and the artificial line, in this quadruplex system, are sim- 
ilar to others already described. 



GENERAL REMARKS ON THE QUADRUPLEX. 
Nomenclature — Detectiox of Faults, Etc. 

Nomenclature. — Many of the following terms have been used, and, in some in- 
stances, explained, in foregoing chapters. 

The " neutral" relay is often termed the No. 2 relay ; sometimes the " common " 
relay. The polarized relay is generally called the "polar' relay, or the No. i relay. 
That portion of the quadruplex which causes and responds to the reversals of polarity 
is often termed the No. i "side," that which causes and responds to the increase and 
decrease of current strength, the No. 2 "side." "Reversals" applies to changes in 
the polarity of the battery, or other source of electomotive force, and to the consequent 
changes in the direction of current, and of the magnetism of the relays, etc. The 
"tongue" of the armature of the "polar" relay is that part of it which extends be- 
tween the "contact point" and "back stop." The "tongue" of the "single" trans- 
mitter is the flat spring, with contact point, which is fixed on the insulated block at- 
tached to the lever of the transmitter. The "leak" is the resistance used, in the Field 
key system, between the lever of the transmitter and the ground. The "added" re- 
sistance is that resistance which is connected between the tongue and post of the 
transmitter, and which is short-circuited when the latter is closed. The "tajj" is at 
the junction of the "short " and the "long" ends of the quadruplex battery. 

To "dot". on I, and write on 2, is to open and close the pole-changer, and write 
with transmitter. To "close i" or "2" is to close the pole-changer or the transmitter. 
As the instruments of many quadruplex sets are "bunched" on the table, it is a com- 
mon thing for attendants to use one hand for dotting and the other for "sending." 

A "margin" refers, practically, to the pull permissible on the armature of either 
of the relays without interfering with the working of the instruments. If this pull is 
very little, the "margin" is said to be small. If much, the "margin" is said to be 
large. An increased "margin" is obtained by increasing the ratio of current strength, 
as between key open and closed, and, also, by increasing the total amount of electro- 
motive force used in the circuit. Also, of course, by decreasing the resistance or im- 
proving the insulation of the circuit, etc. The margin on the polar side of a quadru- 
plex may be increased by increasing the number of cells on the small end of the 
battery. 

The term "phantom" is frequently used to denote the circuits practically gained 
by the use of Multiplex systems. For example: One single circuit, say, from New 
York to Chicago, requires the use of one line wire, about 1,000 miles in length. This 
wire, "quadruplexed," gives, virtually, three additional circuits, between those points, 



232 AMERICAN TELEGRAPHY. 

hence it is said those circuits are "phantom circuits," and that the gain is 3,000 miles o^ 
phantom wire ; the latter being generally referred to as phantom mileage. 

The quadeuplex paradox. — While it is true that the successful operation of a 
duplex or quadruplex circuit may be said to depend upon the obtainment of a practi- 
cally perfect "resistance" and "static" balance, it is equally true that the successful 
operation of the duplex or quadruplex, consists in upsetting that balance. In other 
words, the rheostat and condenser of the artificial line balance the main line, as re- 
gards the resistance and. static capacity of the latter ; this balance insures that the 
action of the home transmitting instruments shall not operate the home relays ; but 
the distant battery, or resistance inserted in the main line, upsets this balance, and, 
thereby, operates those relays. 

Balancing the quapruplex. — The "resistance" balance, generally speaking, 
consists of placing in the artificial line, by means of the rheostat,a resistance equal to that- 
of the main line wire, the distant relays and the distant battery. 

The "static" balance consists in giving to the condenser attached to the artificial 
line a "capacity" equal to that of the main line. In some instances a con- 
denser has been so connected with the main line and a third coil of the relays (for ex- 
ample the Gerritt Smith arrangement), as to compensate, fairly, for the static effects of 
the line. In other cases an induction coil has been placed in the main and artificial 
lines (for instance, the F. W. Jones device)f and so connected with a third coil in 
duplex relays as to compensate for the static effects of the line upon them. But, so 
far as known to the writer, the only device employed for the purpose at present is the 
Stearns arrangement of the condenser, shown in the figures illustrating the vari- 
ous duplex and quadruplex systems described in previous chapters. 

To balance a quadruplex, ask the distant station to "ground." This he does by 
turning the 3-point switch to the "ground" point. The home station then "grounds" 
also, and proceeds to put the "tongue" of the armature of the polar relay on its 
"centre." When this is done the armature will stay on whichever side placed. TJie 
home station then "cats" in his battery, by turning the 3-point switchto the "line"point. 
The No. 2 transmitter is then closed, and the pole-changer is opened or closed, and the re- 
sistance of the artificial line is changed until the armature of the polar relay remains 
on either side. It is well to see that this resistance balance is the same with both 
poles to the line. If it is not, and if the difference is not very marked, the average re- 
sistance of both poles may be used. The distant station may then be asked to cut in 
and to open his transmitter. This, as a rule, places the "short" end of his battery to 
the line. In some cases where a repeating sounder is not used on the ISTo. 2 side, the 
short end is placed to the line when the transmitter is closed. It is sometimes found 
desirable to thus arrange the- battery connections. When the short end of the distant 
battery has been placed to line, the home station may proceed to take a static balance. 
First, by putting his full battery to the line, and then by adjusting the condenser until 
the polar relay does not respond to the opening and closing of the home pole-changer. 
Afterwards, the home station lets down the spring of the neutral relay, until it rests 
lightly on its back contact point. 

The opening and closing of the home pole-changer is resumed, and the condenser, 
or condensers, and their resistances, are adjusted until the "kick" on the neutral relay 

" Neither of which is described here. 



NOMENCLATURE. S2>3 

is eliminated. * It will be difficult to get rid of every trace of tMs *'kick" when the 
armature lever is only held on its back contact by a very slight pull of its retractile 
spring, but, if the armature is passive on its back contact on a much slighter pull of the 
spring than is required to withdraw the armature from its core when the entire distant 
battery is to the line, it may be safely assumed that a good static balance is 
obtained. 

The balance may be taken altogether on the No. 2 side, if desired, but, by taking the 
preliminary balance on the No. i side, it leaves the polarized relay ready for work 
without further adjustment. 

It will be noted that with the sma// end of the distant battery and the /////battery 
at the home end to the line, the nearly maximum static effects are compensated for at 
the time when the home relays are in their most sensitive condition, and, if the balance 
is maintained at that time, there will not be much likelihood of its being affected when 
the entire distant battery is to the line, since at that time the armatures of the home 
relays will be most strongly held in their respective positions towards their cores. 

When the "resistance" and "static" balances have been obtained, the distant 
station should be asked to "write on both sides," while the home station does like- 
wise. While this is being done, the neutral relay may receive any necessary adjust- 
ment. 

Causes and symptoms of faults on duplex and quadruplex circuits, and meth- 
ods OF detecting them. — To insure the successful working of a quadruplex circuit, con- 
stant attention to details is essential. One radical defect in a quadruplex or duplex 
circuit, may be readily traced and eliminated, but many trifling defects, allowed gradu- 
ally to accumulate, and not one of which, perhaps, by itself, would seriously interfere with 
the working of the system, may, jointly, cause trouble which will be much more diffi- 
cult to locate than the one radical defect. 

Frequently, on entering an office, while on an investigating tour of circuits, the 
writer has been met by the official in charge with the assurance that everything under 
his supervision was in excellent order. The writer having satisfied himself, by careful 
tests of the circuit from a distant station, that there might be ground for thinking 
otherwise, would usually proceed to overlook matters. An examination of the main bat- 
tery would perhaps indicate that the major portion of that important element of a duplex 
or quadruplex system was in fair condition, but, possibly, on one of the top shelves, two 
or three defective looking cells would be discovered. The battery man on being 
questioned would probably admit that recently a local battery of an important circuit 
had suddenly given out, and he had, just temporarily, taken out two cells from the 
quad battery, and substituted defective "locals" for them. He had much better haA^e 
left them out. Next, the local batteries would be investigated, and a suggestion of a 
change here and there would be acted oipon. Possibly two or three of those cells had 
been allowed to become practically "short-circuited" by an accumulation of salts; or 
the insulation of the copper connecting wire liad been abraded, permitting the wire to 
touch a zinc, etc. The "quad" instruments woidd next be inspected; a loose contact 
tightened in one place; a dirty contact point cleaned; in one instrument a worn out 
spring would be replaced ; in another the points of contact would perhaps be more 
correctly adjusted, and a number of other different details, seemingly trifling, would 

* It may also tend to a better balance if the distant pole-changer is opened a;;;, ckised at intervals. 



234 AMERICAN TELECxRAPHY. 

receive attention. The distant station would then be called up for a test with the 
quite frequent result that he would report a satisfactory working of the set. 

If, after a careful "balance,'* the signals of tlie distant station are obscure on either 
"side" of the quadruplex, the symptoms should be noted, and steps taken to remove 
the cause. 

The causes producing, or conducing to, imperfect signals, are many, and it would 
be difficult to mention all of them. Indeed, new causes of faults, that cannot well be 
foreseen, are every now and again developing, and it is only by tracing such faults to 
their source, step by stejD, that they can be located. There are, however, many fre- 
quently recurring troubles, which are manifested by well-defined symptoms, and a 
few of them will be alluded to here. (It will be understood that reference is now had 
to the gravity battery quadruplex key system.) Other faults of less frequent occur- 
rence will be indicated subsequently. 

As already mentioned, or intimated, in several places in this work, much of the 
trouble in the practical operation of duplex and quadruplex circuits, automatic re- 
peaters, etc., is occasioned by the failure to look after, properly, the condition of the 
contact points, local and main, of the different instruments. 

In addition to the high resistance introduced at the contact points by the produc- 
tion of oxide, due to sparking, (already referred to) dust, and pieces of feather dusters^ 
at times get between the contact points. When this happens at the pole-changer, it 
will be indicated at the distant station by his failure to get one or both of your 
"poles" properly, or it may simply act to render his received signals unsteady^ 
When it occurs at the transmitter, it may prevent the long or the short end of the 
battery from reaching the wire, or it may open the circuit altogether. Similar causes- 
also frequently impair the working of local circuits. 

If a general overhauling of your contact points, etc., fails to improve your signals 
at the distant end, the home battery should be tested. This may be done by the aid 
of the home quadruplex or duplex instruments, opening the main line to facilitate the 
test. The line wire may be opened at the switch- board, or by detaching the line wire 
at its point of connection with the desk apparatus. The currents from the home 
battery will now joass through but one coil of the home relays, and the effect upon 
those relays should be the same as that previously observed at the distant end. 

Assuming the line wire to have been in proper working order, the home station^ 
by opening and closing the pole-changer, with the transmitter open and closed alter- 
nately, may see and "feel" for himself, by the pull of the magnets, whether the cur- 
rents pass with equal strength from both poles of his battery. He can also see whether 
the "long" and "short" ends of his battery pass to the line, by the action upon his. 
neutral relay. If not, the reason may be definitely ascertained by tracing back from 
point to point. Sometimes the wire between the battery and switch-board is broken;, 
sometimes a wire under the base-board of instruments; sometimes a loose screw exists. 
Again, it may be a broken wire in the battery, etc. Possibly it may be a faulty con- 
nection in or about the line coils of the relays. If so, the previous tests would not 
hiive shown it. To insure that such is not the case, the artificial line should be con- 
nected to the main line post on the polar relay, so as to test those coils, the artificial 
line coils being left open in the interval. Or, the line wire may be connected as usual. 



FAULTS IN QUADRUPLEX. - 235 

and the artificial line wire disconnected; the line wire being grounded at "distant" 
station during this test. The writer has found this method very effectual, as it en- 
ables the attendant at the home station to determine for himself, by the various 
manipulations of the transmitter and pole-changer, what he would, otherwise, only 
ascertain by questioning the distant station as to the results of such manipulations* 

Of course, if the attendant at the distant end is more expert than the one at the 
home station, it may be well to permit him to dictate as to the manipulations of the 
keys, and if possible, to locate the defect from the distant station. 

A differential galvanometer in the circuit is very useful in making such tests, as it 
will show at a glance, whether, or not, each pole of the battery or of the dynamo ma- 
chine is coming properly to the instruments, and also whether the proper increase and 
decrease of current is being effected by the transmitter. 

Even after everything has been proven to be all right at the home station, it may 
be that signals are not satisfactorily received at the distant station. It being assumed 
that the attendant at the latter station has overhauled his own apparatus, it will then 
be well to change the wire for one known to be indefective. The trouble still remain- 
ing, another quad, set, also known to be in good working order, may be tested against 
the supposed defective one. Indeed, it is often desirable to do this immediately on the 
appearance of any not easily explained trouble, as it at once locates the fault in one 
set or the other, or in the wire. 

When no amount of adjusting of the condenser will balance the line ^'static," the 
cause may be looked for in or around the condenser, especially if no noticeable effect 
is produced by alterations of the capacity of the condenser. It may be that the wires 
connecting that instrument to the artificial line, or to the ground, are loose or broken; 
or the plates of the condenser may have become crossed; this latter, however, unless 
the cross is only partial, and has a comparatively high resistance, would act like a 
partial ground, as there would only be the resistance of the "retarding" resistances 
between the battery and the ground, and, in that case, a balance of the line resistance 
would scarcely be possible. A somewhat similar effect would be caused by the burning 
out of coils of the "artificial line" rheostat. 

Sometimes, also, a static balance is rendered difficult by the presence of a wire 
crossed at some point of the duplex or quadruplex circuit, and open at both of its ends, 
thereby adding its "static" charge and discharge to that of the regular line. To offset 
this trouble, a second or third condenser may be necessary, together with a careful 
adjustment of the retarding coils. 

One obscure source of trouble is sometimes due to an abnormal variation in the 
resistance of one or other of the coils of the relays. It is a good plan to have some 
spare relays well " balanced," and known to be in perfect condition, ready to replace 
any corresponding relay whose faultlessness is suspected. The same is also advisable 
as regards pole-changers and transmitters. 

In order to ascertain whether a relay is properly balanced, that is, whether, with 
equal currents passing through both coils in opposite directions around the core, its 
armature will remain passive, the relay should be tested by itseif with a strong bat- 
tery; for which purpose it may be connected up as indicated in Fig. 183^7. The coils 
are connected at their respective binding posts by short pieces of wire 7C', 7c>, and 



236 



AMERICAN TELEGRAPHY. 



FIG. 183. 



the terminals of the battery are momentarily touched to those wires. This sends 
the current through the respective coils in opposite directions. With a well balanced 
relay there should not be more than a very faint movement of the armature ; it being 
adjusted close up to the core and resting on its back stop with its retractile spring 
almost dangling. This refers to the neutral relay. When the polarized relay is to 
be tested its respective coils are connected and the battery terminals are applied iu 
the same way, the cores being moved close up to the armature on both sides. When 
a decided movement of the armature is noticed under these conditions the relay should 
be sent back for correction or repairs. 

When making th^se tests the movement of the armature, or its lever, should be 

free and easy on its bearings. The attendant 
should also, of course, be on his guard to note 
that the terminals under the base of the respec- 
tive coils of the relays are connected to the 
proper posts to produce neutrality in the cores 
'^f'^^^W^ O when equal currents are passing through the 
coils. It sometimes happens that a relay con- 
nected up in an unusual way is permitted to 
pass the inspectors at the factory and thus be- 
comes a marked source of trouble unless the 
cause is quickly discovered. This remark is 
equally true of unusual connections under the 
bases of pole- changers and transmitters. 

The resistance of the coils should also 
be measured, although it will almost al- 
ways happen that when the "balance" of a relay is found to be accurate, the resist- 
ance of both coils will be, within a very small fraction, equal. It is not, however, 
to be taken for granted th^t such is the case, since it is possible that a portion of 
one coil might be short-circuited to just the extent necessary to divert enough 
additional current through the remainder of the coil to compensate for the dimin- 
ished number of convolutions due to the short-circuit. 

Tests should also be made to determine whether any "cross " exists between the 
coils, or between either of the coils and the iron core. This is done by disconnecting 
all external wires from the posts of the relays and then applying the terminal wires 
of the battery to a binding post of two different coils : then to the binding post of 
a coil, and to the iron of the core. A " cross ' ' will be indicated by a spark at the 
points of contact, or by a movement of the armature lever. 

When the distant " reversals " break up the received signals on the No. 2 side, 
a new balance may be required; the distant pole-changer may need adjustment, or 
the retractile spring of the home neutral may require letting down. When the re- 
versals caused by the home pole changer interfere with received signals at the home 
station, anew general balance may be needed; possibly only a static balance. Or 
the trouble may be overcome by pulling up the retractile spring of the No. 2 relay, 
provided that this action does not bring the armature within the scope of the di's- 
tant reversals. The advantage of a good working margin on the No. 2 relay is that 




FAULTS IN QUADRUPLEX. 237 

it permits a readily found happy medium, between these two " effects " : namely, 
that due to the distant and to the home reversals, respectively. 

Perhaps the writer cannot better illustrate some of the less frequent causes of 
trouble in quadruplex working than by quoting from his personal notes the results 
of an inspection of a series of quadruplex circuits extending over a distance of 
nearly fuui- thousand miles. 

The circuits were all newly established, and in one or two instances the at- 
tendants had never seen a quadruplex set previously. At the first station a, nothing 
radically wrong was discovered, but a number of minor details had been overlooked 
and it was evident from the report of the eastern station that improvement was 
observable after they had received attention. At the next station, b, the attendants 
were quite sanguine that the trouble was in a_^ ^tliat being a railroad office. Pres- 
ently the writer chanced to see on one of the desks an instrument used in certain 
experimental tests with which he was familiar. It was a magnetic coil having a re- 
sistance of 500 ohms. On asking the number of the circuit allotted to the desk in 
question the reply confirmed the suspicion that it was the "defective" circuit. The 
coil was removed and the circuit was tested without it, whereu^wn station a reported, 
as was to be expected, that the circuit now worked admirably. The magnetic coil had 
been placed in the circuit during the experiments alluded to, and^ was allowed to re- 
main therein subsequently, its detrimental effect upon the circuit not having been 
surmised. 

Tests were then continued between b and c, with the result that an increased 
ratio of current strength was advised; the wires between b and c having high resist- 
ances as compared with other circuits working with similar electromotive force. At 
c, nothing was discovered except as to minor details. But at c the manager at d 
reported, over the wire, a complete failure of the circuit south of him. He stated 
that E office insisted that his, d's, " tap" wire, was open. Tests made from c showed 
that this was not so. 

It was raining heavily when the writer reached d and the No. 2 side of the quad, 
south, was useless. This was at first attributed to defective insulation due to the wet 
weather, and further action was delayed for one day to give time for the Avires to 
" dry off. " This the wires north did upon the appearance of clear weather, but the 
low insulation south, which almost amounted to a "ground," still continued, notwith- 
standing that the fair weather now extended all along the line. This being so, a 
close personal inspection of the line was determined on. It should, in fairness, be 
said, in advance, that this telegraph line had just been taken over from a " Con= 
struction " company and had not, previously, been inspected. 

Three or four miles from the station, what seemed to be a very luxuriant vine, 
growing up one of the telegraph poles was perceived. Examination showed that 
this foliage had sprouted from the pole and was festooned around the wires for a dis- 
tance of 3 or 4 feet in each direction. Several poles were found similarly sprouting. 
The poles were native saplings which had not been peeled and which grew 
wlierever stuck in tlie ground. After these "decorations'* had been removed the wire 
assumed a normal insulation resistance, and the manager at d was pleased to bo 



238 AMERICAN TFLEGRAPHY. 

able to prove that his "tap wire" had not been broken, tlie more especially as he 
was not responsible for the "foliage." 

At E, fair weather prevailed, and not much of importance was noted. At f, the 
batteries were in a deplorable condition, due to climbing salts, and, notwithstanding 
that water was difficult to obtain in large quantities, oil had not been used to prevent 
evaporation, owing to the belief that oil would "grease" things. Between f and g 
there was a radical defect. The insulation resistance of the line was fair and the 
resistance of the wire was also normal, but there was no working margin on the neu- 
tral side. 

On reaching g investigation showed, as anticipated, that the " tap " was on the 
wrong end of the battery, so that, instead of having a ratio of, say, 4 to i, there was 
a ratio of but 4 to 3, as between transmitter open and closed. When this fault had 
been removed the circuit worked perfectly between f and g. 

General remarks: — When there is a number of parallel circuits in active opera- 
tion the opening and closing of each circuit sets up induced currents in the other cir- 
cuits, the strength of which depends upon the nearness of the other wires to the '' in- 
citino"" wire, the distance it runs parallel with them, and the electromotive force of 
its battery. 

In taking a balance on a duplex or quadruplex circuit, under such conditions, a 
very pronounced clatter is generally heard in the relays, especially in the polar relay, 
as long as there is no current on the circuit in question, at either end, and also after a 
balance has been obtained, but before the distant battery is placed to the line. 

If, with the small end of the distant battery to the line, either of the relays 
should be affected by the currents induced by parallel circuits, and there is no rea- 
son to think that the battery is not in working order, it is fair to assume that higher 
voltage is needed on the short end, at the distant station. 

in practice it has been found by the writer, repeatedly, that up to a certain num- 
ber of circuits, say four or six, each additional circuit necessitates increased voltage 
on the other circuits, but that, after that number has been reached, the placing of 
still more circuits does not materially affect the working margin. 

The high voltage used on quadruplex circuits, (which is from 3 to 4 times that 
needed on single or duplex, circuits of equal length,) of course, necessitates that the 
minimum electromotive force used on the "short" end of each circuit should fur- 
nish current sufficient to hold the armatures of the relays firmly against their storps 
against the inductive effects due to the rise and fall of the maximum "currents" 
on parallel circuits. 

The writer recalls the case of a polar duplex circuit, 432 miles in length, which 
was successfully worked with 40 volts at each end when first established, but which 
I'equired, for its proper operation, 100 volts at each end, after a luiraber of quadruplex 
circuits had been established parallel with it ; the electromotive force of the latter 
circuits was about 370 volts at each terminal station. These, and similar results on 
other circuits, could not be attributed to surface leakage, that is, leakage from wire 
to wire, via the cross-arms, poles, etc., as the effects were, if anything, more marked in 
cold, drv weather, than in stormy weather. 



RULES FOR MANAGMENT, ETC 239 

These causes seemingly preclude the use of any hard and fast formulae as to the 
amount of current necessary to successfully operate such circuits, inasmuch as the 
laboratory 'figure of merit " of an instrument would not hold where these coun- 
ter electromotive forces have to be allowed for. 

The ordinary resistance of the quadruplex neutral relay is about 225 ohms, but on 
very long circuits a resistance of about 400 ohms has been found advantageous ; the 
added resistance, of course, being made up of increased convolutions of wire. 



Any one who has had much to do with the practical working of duplex and 
quadruplex circuits will not have failed to observe the waste of time that is frequently 
caused auring the prevalence of stormy weather, and at other times, by attempts to 
operate, to their full capacity, circuits tliat for various reasons are not in condition to 
be so operated. 

Sonu times it is the case that, owing to the particular conditions existing at 
the time, one station may be able to work his set "all sides, " while the other station 
may not be able to get more than a duplex or triplex, and it is not always easy in 
those cases to make it clear to the successful "attendant," who perhaps insists on 
working tlie circuit 4 sides, that the result at his end is not due so much to his ex- 
pertness as to the circumstances. 

These and other causes led to the formulation of the following rules by the 
writer for the government of an extensive duplex and quadruplex system, of which 
lie had the supervision. 

These rules, which are, perhaps, self-explanatory, were admitted by all concern- 
ed to be beneficial and it may be that they will serve as a basis of rules for others 
who may appreciate the need of somewhat similar systemization. 

"rules fok the management of duplex and quadruplex circuits in case op 
instrumental or wire trourle, or during stormy weather. 

When intricate trouble occurs on any duplex or quadruplex circuit that cannot 
be eliminated within 30 minutes, at the end of that time the circuit must be started 
as a duplex, if it will work as such, or, if not, as a single wire ; unless the circuit can 
be readily dispensed with for a longer time. 

When the attendant at. either end reports to the distant station that a quadruplex 
circuit will not work as a full quadruplex this will be sufficient basis for the abandon- 
ment of so much of the quadruplex as may be thus rendered necessary, even although 
the other attendant may be able to work the circuit to its full capacity. The at- 
tendant ordering thLS partial abandonment of a circuit will be held responsible there- 
for, and must, if required, be able to show sufficient cause for the same in every case. 

No time should be lost discussing the advisability of or necessity for balancing 
changing or testing wires, cutting through, as at repeating stations, etc. If one sta- 
tion asks another to balance, change or test wires, cut through, etc., the request should 
be complied with, at once. This rule will, however, not apply where the entire con- 



^4C> AMERICAN TELEGRAPHY. 

trol of circuits has been conferred upon any one of the offices. But it will be the 
right and the duty of the subordinate office to report to the proper official any ap- 
parently useless requests for balance, etc. 

Quadruplex attendants should carefully record the condition of the wires under 
which the various circuits in their charge will not work satisfactorily either during prev- 
alence of very bad weather, or when a circuit is " patched " with an inferior wire, etc., 
so that no time may be wasted in futile attempts to obtain more service from a cir- 
cuit than it is capable of performing, under recurrences of similar conditions. These 
records should be easily accessible to all concerned. 

Attendants also, at terminal stations, should mutually inform each other of any 
changes in the weather that might necessitate alterations in the balance and adjust^ 
ment, thus anticipating or explaining trouble. 



The Roberson Quadruplex. 

It is well known that on long lines, and especially in bad weather, the second or 
neutral side of the Edison quadruplex is not as efficient as the polar side. The chief 
object of the Roberson quadruplex is to secure a system both sides of which shall be 
equally efficient under all conclitioiis. To secure this result, Mr. 0. E. Eoberson, to 
whom this arrangement is due, has found it necessary to employ current pulsations 
of positive and negative polarity in place of the comparatively continuous currents 
used on the polar side of the Edison quadruplex, and the nearly continuous currents 
used on the neutral side; it being known that the characters received on the latter 
side are somewhat broken by the signals transmitted on the polar side; not, however, 
to such an extent as to be observable or detrimental on a good working quadruplex. 
0]i the other hand, it has been noticed that the signals composed of a number of pul- 
sations — as, for example, in the synchronous multiplex system described herein — have 
a wavering or fluctuating sound, not common to the single Morse or quadruplex sys- 
tem. This feature of rapidly pulsating systems, it is claimed, has been largely min- 
imized -in the system in question by the devices to be described, and, in any event, 
the bad- weather qualities of this system are so superior that it is now being put into 
operation on a number of the lines of the Western Union Telegraph Co. 

The theory of the Eoberson quadruplex is shown in Fig. 183^^ To simplify the 
explanation, it may be noted that the first principles involved in the operation of this 
quadruplex are similar to those of the Sieurs diplex, described in Chapter XVI. In 
the ai)plica[ion of these principles to the qur^druplex and a dynamo key system, sev- 
eral difficulties were encountered which Mr. Eoberson has successfully overcome. 

'i'he negative and positive pulsations which are transmitted to the line when one 
or other of the transmitters is closed, as well as the alternations of polarity which 
are transmitted to the line when both are closed, are generated by the dynamo, x, s, 
Eig. i83«, on the shaft of which are three rings, ^, c, d, which revolve with it. One 
half of the rings, c, ^/, is insulated as shown by the black dashes. This insulated half 
of the ring is mainly of metal, to give a good wearing surface for the brushes. The 



THE ROBERSON QUADRUPLEX. 



240^^; 



other half of these rings, which may be termed the conducting segment, is entirely 
of metal. The brushes 4 and 3 respectively rest on opposite sides of the ring c. 



FIG. 183a. 



LINE 




/ 
/o 


1^ 


i 


i 


^.?.ia^v 












i: 







THE ROBERSON QUADRUPLFX-THEORY. 



The conducting segment of e is connected by wire i to one terminal of the armature cf- 
of K S; the other terminal of this armature is connected to ground by way of ring b 



240^ AMERICAN TELEGRAPHY, 

and wire lo. The conducting segment of d is ulso connected to ground byway of 
wire 7, ring b, and brush lo. Eing b is entirely of metal. Wire 7 and the wire i 
of course revolve with the shaft and are securely held in place close to shaft. Eing 
h is continuously connected to ground by the brush 10, and its function is to provide 
a ground connection for the other rings and armature. 

Assuming that in the position of the armature of the dynamo as shown in the 
figure, the brush 4 is receiving positive polarity from the conducting segment of c, 
it is well known that when the armature and segment have turned to the opposite 
side of their revolution a negative polarity will be received by brush 3 {see page 44). 
Hence the brush 4 will always collect positive, while the brush 3 will always collect 
negative polarity, and of course no current will pass into the brushes while resting on 
the insulating segment of c. 

Eef erring now to the transmitters m m\ it will be seen that the lower left-hand 
contact point of m is connected by wire 11 with positive brush 4 one; the lower left- 
band contact of m' is connected by wire 13 with negative brush 3 on c. Also, that 
the lower right-hand contact point of m is connected by wire 1 2 with brush 2 on ring 
d\ the lower right-hand contact of m' with the brush 5 of same ring by wire 14. 
Hence, when either or both of the transmitters are closed, negative or positive pul- 
sations or alternations of both will pass to line, and when either or both are open the 
line is intermittently placed to ground direct via brushes 2, 5 and the ring h. 

The conducting segments of c and d cover slightly more than half of the periph- 
ery of the ring, which insures that contact will be made by one brush before it is 
broken by tho other: but as at the instant when botli brushes are on the conducting 
segment the potential of the armature is zero (see page 44), no sparking will follow. 
At other times the insulated portions of the ring prevent short circuits between the 
brushes. 

The Limps or other resistance shown in wires 11, 12, 13, 14, and a carbon rod 
resistance 0', are inserted for the usual purpose of avoiding injury to the relays and 
other apparatus in case of grounds. The resistance of the lamps in wires 11 and 13 
is about 50 ohms; those in wires 12 and 14, about 100 ohms. It is clear that it is 
not advisable to place high resistances between the dynamo and transmitters, inasmuch 
as such resistances are placed in multipe when brushes 4 and 3 are on the conducting 
segment of c, and this would have the effect of varying the balance at the distant 
end. The resistance of the carbon rod 0' may be from 500 to 1000 ohms, depending 
on the voltage used: on the longer circuits it is about 1000 ohms. Fuses, not 
shown here, are also placed between the dynamo and transmitters to protect the 
armature in case of short circuit at transmitters. The E. J/. F. of dynamo x. s. is 
about 200 volts. The resistance of armature a is about 50 ohms for long circuits. 
A non-inductive resistance — that is. a coil wound back upon itself {see Eheostat) or a 
carbon rod r i\ of about 6000 ohms, is inserted around the front contact 23oints of 
each transmitter. This permits weak current pulsations to pass to line when the 
transmitters are open, for a purpose presently to be explained. The condensers c c, 
and small resistances not shown in the figure, are employed around the front contacts 
of transmitters to diminish sparking at those points. It is found that very little 
capacity in the condenser is required to effect this result. It would not be advisable 



THE ROBERSON QUADRUPLEX. 240^ 

in this quadriiplex to use solenoids such as are shown at R, Fig. 24, as resistances, 
for, apart from their bulk, their magnetic effects would, owing to the rapid varia- 
tions of current, produce an impedance that would be detrimental to the operation 
of the system. Hence the use of carbon rod resistances which have no noticeable 
inductance. [See Self Induction, page 100.) 

In practice, as this quadruplex is operated by the differential method, the receiv- 
ing relays a b are differeutially wound. The relays are of the Huglies polarized form, 
this form having been found to be best adapted for this work. The Hughes relay 
differs from the well known form of polarized relay employed in the polar duplex and 
the Edison quadruplex, in which the cores of the electromagnet audits armature are 
joined to opposite ends of a permanent horseshoe magnet. The main difference is 
that only the cores h li of the electromagnet are connected to the permanent magnet, 
g, as shown more clearly at the left of Fig. 183^^. This arrangement of the permanent 
magnet gives the cores li li a certain magnetism, one becoming a north pole, the 
other a south pole. The coils of relays A b are then so connected that a certain cur- 
rent, say a positive current, will assist the induced magnetism of one, let us say a, 
and oppose the induced magnetism of the other relay b; whilst a negative current 
will assist the induced magnetism of b and oppose that of A. The armature of each 
relay is provided with a suitable retractile spring as shown, the tendency of which is 
to withdraw the armature from iis core, and the spring is so adjusted that it over- 
comes the induced magnetism of the cores (and the weak open transmitter currents 
to be referred to). When, then, a current passes through the coils in such a direction 
as to assist the induced magnetism of a relay, its armature is attracted; when the 
direction of the current is such as to neutralize the magnetism of the cores, the 
armature is not affected and remains on its back stop. 

The permanent magnet of this relay is usually provided with a movable " keeper '* 
(a strip of soft iron), which may be shoved up and down across the legs of the mag- 
net, and in this way short-circuits or diverts more or less of the magnetic lines of 
force from the ends of the magnet, thereby increasing or decreasing the induced 
magnetism in the cores of the relay as desired. The nearer to the ends of the per- 
manent magnet the keeper is brought, the less will be the induced magnetism in the 
cores. In practice the keeper is usually kept close to the cores, although in wet 
weather it is found advisable to raise it somewhat, in order to admit more lines of 
force into the cores, the proper distance being found by actual trial. 

The chief advantage of the Hughes relay is its sensitiveness to weak currents 
and its quick action. Its sensitiveness, in common with that of the ordinary polarized 
relay, is largely due to the fact that the magnetic pull of a magnet on its armature is 
proportional to the square of the number of lines of force in action. Thus, if the 
induced lines of force in the cores due to the permanent magnet, number, say, 100, 
and if the number of lines due to the effective current flowing in the coil, be, say, 
100, we have apullin the first instance proportional to the square of 100, or 10,000; 
and in the second instance we liave a pull proportional to the square of 100 -j- 100. 
or 40,000. Thus, in wet weather, when the received current is reduced by escapes on 
the line, the pull on the armature may be increased somewhat by increasing the in- 
duced lines of force, although the gain to be obtained by this means is limited by the 




^^Od AMERICAN TELEGRAPHY. 

counter-effect of the added pull necessary to be given to the retractile spring to with- 
draw the armature of the relay when its distant transmitter is open. 

The alternations of polarity generated by tlie dynamo :n' s are at the rate of 40 per 
second or 2400 per minute. 

The armatures of relay A and b are each furnished with an extra magnet and 
n respectively. The coil of n is in multiple with the repeating sounder q, and both 
are controlled by the lever of b. Similarly the coil of is in multiple with the re- 
peating sounder^;, and both are controlled by the lever of A as shown. These repeat- 
ers act as so-called " bug^' catchers, as in the Edison quadruplex, t and s being the 
ordinary sounders. In a later arrangement, the repeating sounders p q have been 
replaced by a repeating sounder of the form shown in Fig. 
i8;^b. In this, R s has two levers, the lower one of which 
( f \ has the local contacts of sounder s. The lower lever is 

y I ^ J I ^ 1 operated by the upper Jever, which itself is operated by the 

magnet. The object of this device is to make it necessary 
for the upper lever to traverse a considerable distance down- 
ward before it will push the lower lever away from the con- 
tact i, thereby to more effectually prevent false signals on 
sounder s due to a momentarily prolonged contact of the lever of A or b on the 
back stop. 

It maybe seen by reference to Fig. 183^?, that when, for instance, the armature 
lever of a is on its back stop, the magnet is magnetized by the local battery of n, and 
that when the lever of b is on its back contact point n is nnignetized by the local bat- 
tery of 0. The object of using these extra magnets is to obtain a practically uniform for- 
ward pull upon the armatures of the relays at the times when but one or when both 
of the relays are in operation, for it is well known that successive pulsations of one 
polarity more fully charge the line and magnetize the cores of a, relay than do rapid 
alternate positive and negative pulsations of current, and in this system, if this effect 
were not guarded against, signals varying in strength, or wavering, would result 
(see page 288). The effect of the operation of the extra magnets is to weaken the 
forward movement of the armature when but one relay is working. For example, if 
relay a, which we will say is responsive to key k, and thus to positive pulsations of 
current, is in operation alone, its forward movements will be weakened by the back- 
,ward pull of n, whose local circuit is then closed at the back contact of b; and if B 
alone were in operation its forward movements would be weakened by the backward 
pull of 0, whose local circuit is then closed at the back contact of A. When, on the 
other hand, both relays are responding to pulsations, namely, when both keys k, h' 
are closed, and in consequence their armatures are in rapid vibration, the time of 
contact on the back contact is so slight, the extra magnets n as well as the repeat- 
ing sounders remain inoperative, as mentioned in connection with the Sieurs diplex, 
page 2 66«. The j)nrpose in sending weak currents to line when either transmitter 
is open is also to maintain approximately the same forward pull upon the armatures 
whether either or both of the relays are in operation, a weak positive current follow- 
ing a strong negative current, or vice versa, tending to accomplish the desired object, 
since by so much it clears out the previous charge (see double current, page 288), 



THE ROBERSON QUADRUPLEX. 240^ 

The emploTUieiit of these devices has been found to have a steadying effect upon the 
relays. 

The coils of the relays a b are connected in multiple, there being two coils of 
300 ohms each, thus giving a joint resistance of 150 ohuis for the main and artificial 
line coils {see multiple wound relays, page 317)- 

It may be noted that by adding additio]ial rings on the shaft of x s other 
Roberson qiiadruplex sets could be supplied with current from this machine.* 

To B.\LAKCE THE EoBERSON Qx^iDRUPLEX — Mr. Roberson gives the following 
as the best metliod of balancing this system. 'J^he balance maybe made with either 
relay, but as the rheostat and condensers are on the "a" side, that side is generally used 
for balancing. First, request the distant station to open both keys, which places the 
line to ground through the resistance 0' and the lamps or fuses. Then open both of 
your keys, after which turn down the spring of A relay till the lever stays oii either 
the front or back stop, or until it vibrates, by the line induction or weak distant 
pulsations between them. Then throw the 3-point switch s w to the left, which 
places a battery or dynamo d c, famishing direct current of say 320 volts to the 
line. If the line is out of balance the armature of relay will now be attracted. Ad= 
just the rheostat R in the artificial line /, as in the case of the Stearns condenser or 
the Edison quadruplex, until the armature remains on either front or back stop as 
before. Now throw the 3-point switch back to its left-hand point, and pull up a 
little on the retractile spring of the relay, until the lever rests lightly on its back 
contact point. Then close both your keys k k\ which puts alternations of full 
strength to line. If now the arm^ature of relay is affected it shows that the static 
balance is out. Therefore now adjust the condenser or condensei's c" (if there are 
more than one) and the amount of lesistance in the " retarding^' coils r' until the 
lever stays on its back contact. Slight variations in the condenser or resistance will 
sometimes effect this result. Then have the distant station close his b transmitter 
and write on A transmitter, and adjust your A relay until the signals arrive satisfac- 
torily. Then have him open transmitter A and write on B, when, if signals are not 
as clear as before, adjust the extra magnet on your A relay until signals are satisfactory. 
An adjusting screw practically similar to that used on the Morse relay (Fig. 44) is 
provided on the extra magnets for this purpose. If signals are light, screw the mag- 
nets back ; if heavy, forward. Then, if necessary, do same on B side, but changes 
on that side of this quadruplex are not often required. 

When signals fail to come properly after a careful balance has been taken, it is 
advisable to examine contact points of transmitters to see that they are in order; test 
line wire, apparatus, etc., as in case of the Edison quadruplex. The apparatus may 
be entirely disconnected from the dynamo by throw^ing a switch, similar to c s in 
Fig. 180, to the right, which switch is arranged on the desk for this purpose. 

* A device shown in theory jn Fig. 183c at left of Fig. 183a, has recently been introduced, whereby the alternating 
generator n s, Fig. 183a, is replaced by a commutating ring r, and brushes b, b\ c, giving currents of different polarity from 
direct current machines, indicated by d, d'. Ring r is on shaft m which is rotated by a motor. A segment <«•■ on one side 
of the surface of r is insulated, as shown. The brushes b b' are so placed that while one is on the insulated surface •'•. 
the other is on the conducting surface ,s^' of the ring. Brush c connected to line is always on the conducting surface cf 
the ring. Consequently, when brush b is on s\ and transmitter rn is closed, positive pulsations pass to line. When brush 
b' \s on s' and transmitter m' is closed, negative pulsations pass to line ; when /n and //i' are closed, alternations of 
polarity go to line ; when ?n aud n are open the line is grounded, etc., all practically as already described. 



240/ 



AMERICAN TELEGRAPHY, 



British Post-office Quadruplex. 



The quadruplex employed on the lines of the British Post-office telegraph is 
shown theoretically in Fig. 183c. This quadruplex is similar in principle to the 
Edisun quadruplex, the only difference being in the construction of the transmittiiig 
and receiving apparatus. The pole-changer and transmitter, or reversiug key ek, 
and increment key ik, as these instruments are respectively termed in Great Britain, 
correspond to the pole-changers and transmitters used here in battery-key systems 
except that they are operated manually by the Morse operator. The reversing key 
KK is shown in end view for clearness ; the increment key IK in side view ; the 
necessary contact points being carried on the end of the lever of the respective instru- 
ments as shown. (See Fig. 160, for example.) The tension contact pieces a a and a a' 
of KK are metallically connected as indicated. The cross-piece e l is insulated in tha 




middle as outlined, e is connected to earth and L to line. It will be seen that as 
the lever I of rk is opened and closed, the entire battery b b', or the short end b 
only, will be rever.-^ed, depending upon the position of the increment key ik. AVhen 
IK is open, as in the figure, only the small end of the battery is to line; when closed, 
the entii'e battery, all in the manner described in detail in connection with Figs. 160, 
161, 162. sis the nsnal 3-point switch for putting the line to ground for a balance, 
etc. sc is a spark coil of 100 ohms inserted to avoid sparking at contact points 
Avhen the full battery is in use. gc is the ground coil, with a resistance equal to the 
entire battery and sc. r is a resistanco in tlie tap wire, made equal to the resistances 
of sc and the long end b' of the battery, to preserve the balance when ik is open. 
NR is a differentially wound neutral relay of the construction indicated, p r is a 
ditferentially wound polarized relay. Each coil of these relays is wound to 200 
ohms. G is a differentially wound galvanometer used as in the Wheatstone automatic 
system for line balancing, etc. R is the usual rheostat or artificial line resistance 
employed to "balance" the main line, c is the static compensating condenser, r' the 
condenser retarding resistance. The armature levers of PR and :n'R operate reading 
and repeating sounders in virtually the manner shown in detail in Fig. 163. The 
polar side of the system is termed the A side ; the increment side, the B side. 

When this quadruplex is used for repeating from one line to another, apparatus 
corresponding to that used in this country is employed, namely, a pole-changer and 
transmitter operated by their electromagnets and keys in local circuits. {See t and 
PC, Fig. 163.) 



CHAPTER XIII. 

DUPLEX AND QUADRUPLEX REPEATERS. 

Although automatic repeaters of the class described are still much used in the 
telegi'aph service in this country, their employment has been largely circumscribed 
by the introduction of duplex and quadruplex systems, which latter, while also re- 



no. 184. 




DUPLEX REPEATERS ARRANGED ON QUARTETTE TABLE. 

pelting automatically from one wire into another, operate in a more direct and 
simple manner than do the "single " wire, automatic repeaters. 



242 



AMERICAN TELEGRAPHY. 



This is explained by the fact that in duplex telegraphy the result is practically 
the same as though two single wires were used, one to send and the other to receive 
by continuously, and as if , when " breaking " is necessary, it should be done on the 
sending wire only. In such a case it is easy to understand that, at a repeating sta- 
tion, the relays of each wire could be made to operate a transmitter controlling the 
battery of another line. This, virtually, is what is done by duptex repeaters, as will be 
seen by reference to Fig. 184, in which pe' and Pc' represent the polar relay and pole- 
changer, respectively, of one duplex set, at a repeating station ; pr and pc represent 
similar instruments of another set at the same station, as generally arranged on a 
" quartette" table. 

It is assumed that pr' and pc' are the terminal instruments of a duplex, working, 
say, east, and pk and pc similar instruments of a duplex, working, west, from the 



FIG. 185. 



T 



fes) 




2V^2 SoLuxde^ 





Ea^^ 



ItejoeaZi/7^ Sozz/ider^ 




-l|l|l|^|l|l 



Single 
TransrTzilter 



W&sf 



Mu^al\^elajr 



-XO. 2 SIDE OF QUAD. REPEATING INTO QUAD. TRANSMITTER OF ANOTHER SET. 



repeating station. The duplex connections are omitted for the sake of simplicity. 
Polar relay pk' by means of its armature lever has control of the local circuit of the 
pole-changer PC ; polar relay pr of the western set, has similar control of the pole- 
changer pc', of the eastern set. By this means whatever signals are received on the 
resDCctive relays are repeated by the respective pole-changers. When it is desired 
to increase the current in the pole-changer coils, the 3-point switch, tp or tp'. is turn- 
ed to the left, which action diminishes the resistance of the local circuit by cutting 



DUPLEX AND QUADRUPLEX REPEATERS. 



243 



out the local sounder. When it is desired to separate the eastern and western sets 
the 3-point switches are turned to the right, which gives each pole-changer and 
polar relay an independent local battery. 

A key is shown on each corner of the table. The key on the polar relay corners 
is placed there to afford the receiving operator facilities for breaking when the sets 
are not used as repeaters. Of course the keys are closed when working through. 

It is plain that the No. 2, or "neutral" side of a quadruplex may be arranged 
in the same general way, for repeating, the only difference being that the contact 
points of the repeating sounder, instead of those of the neutral relay, are made the 
direct means of operating the "opposite " single transmitter. This is shown in Fig. 
185, which, in view of what has been described, will not require further explanation. 

When it is required to repeat from one quadruplex circuit into another, as, for 
instance, in the case of such circuits as those between New York and Chicago, the 

Fig. 186. 




EXTENSION OF DUPLEX OR QUAD. LOCALS TO BRANCH OFFICE. 



first side of each "quad" set is caused to repeat into the first or into the second side 
of the other set, according to the wishes of the " powers that be." There has been 



C44 AMERICAN TELGRAPHY. 

some difference of opinion as to which is the better plan. It is well known that the 
polar side of a quadruplex has a higher working efficiency than the second side, es- 
pecially in stormy weather. It has, therefore, in some cases, been assumed that, this 
being the case, if the good and the inferior sides of the system were interchanged at 
the repeating station, a better average result would be obtained. While this reasoning 
has seemed plausible, experience has convinced the writer, at least, that, on the whole, 
more satisfactory results are secured by repeating from the first into the first side and 
from the second into the second side, in all cases. For these reasons : that, in good 
weather, both sides generally work satisfactorily, and, in stormy weather, the first 
side works tolerably, well, while the second side, as a rule, does not. Therefore, by 
working the sides "straight," at the repeating station, one good duplex is reasonably 
assured, and, possibly, also one mediocre duplex, while, by interchanging the sides at 
the repeating station, the result, in stormy weather is, generally, two very indifferent 
duplexes. 

Extended locals. — It is frequently desirable to extend the local connections of 
a duplex, or one side of a quadruplex set, to a branch office. 

This is done, as shown in Fig. i86, by simply continuing the local wires to the 
branch office. Additional battery is employed to compensate for the increased 
length of wire and the added instruments. 

The wires extending to the branch offices are termed a " loop,'' and the separate 
wires of the " loop " are known as the sending and receiving " leg " of the loop. 
When the 3-point switches, tp, are turned to the right, the " legs " are thrown on to 
the duplex or quad instruments, and are cut off therefrom when the switch is turned 
to the left. This still leaves a local battery for the duplex instruments. Xn the fig- 
ure the instruments are shown idle. 

The connections for this arrangement are shown and explained more in detail 
under the subject of " Loop Switches. " 



Qtjadruplex-Short Wire Automatic Repeaters. 

Sometimes it is not necessary to have more than one " leg " from one side of a 
quadruplex set to a branch office, as when one side of a quadruplex is leased to a 
broker who never uses the wire but one way at a time. 

When this is the case it is evident that some means of keeping the transmitter 
closed, or inoperative, when the distant station is sending to the branch office, must be 
devised. This service can be performed by one-half of any of the ordinary automatic 
repeaters. It was first done, the writer thinks, by Mr. D. R. Downer, as shown in 
Fig. 187. 

THE DOWNER QUADRUPLEX-SHORT WIRE REPEATER. 

In this figure, pc, is the pole-changer; pr the polarized relay of a quadruplex set; 
BT is a repeating transmitter. When the 3-point switch tp is turned to the right the 
circuits are arranged for the working of the quadruplex instruments into the branch 
office. 



QUADRUPLEX-SHORT WIRE REPEATERS. 



245 



111 the figure the local contact of the polar relay is closed. This closes tlie cir- 
cuit passing through the magnet of the pole-changer and the tongue x and post p of 
the transmitter rt, to the branch office. Should the distant station open his pole- 
changer, thereby opening the polar relay PR, it will open the repeating transmitter, 
which opens the branch office circuit at x. Just as this occurs, however, a local 
circuit is formed via the tongue and lever of the repeating transmitter and a small 
portion of the battery b, to and through the pole-changer magnet, keeping the pole- 
changer closed; this forming the automatic feature of the device. Otherwise the dis- 
tant station would get his own writing back. The branch office operates the pole- 
changer by simply manipulating his key, which, of course, opens and closes the bat- 

FIG. 187. 



T ^ U !f o 




DOWNER QUADRUPLEX — SHORT-WIRE REPEATERS. 



tery B. The "Downer" arrangement is generally employed on the Western Union 
Company's lines for short circuits. 

THE GARDANIER QUADRUPLEX SHORT WIRE REPEATER. 

A modification of this arrangement, known as the Gardanier arrangement, shown 
in Fig. 188, was much used on the lines of the Baltimore and Ohio Telegraph Com- 
pany. The operation of this arrangement is easily understood. The larger 
portion e of the loop battery is placed outside of the post of the repeating trans- 
mitter, RT, Wiien RT is closed the loop battery e and local battery lb unite to 
operate the pole-changer and the brancii office instruments. The pole-changer is kept 



246 



AMERICAN TELEGRAPHY. 



closed automatically, when the polar relay is open, as in the figure, by a short circuit 
and the local battery, lb, through the lever and tongue of the repeating transmitter. 
The branch office operates the pole-changer when kt is closed ; the same way as in the 
" Downer " arrangement. 



" EMERGENCY " QUADRUPLEX-SHORT WIRE EEPEATER. 

The " Toye ' ' repeating principle is frequently used as a means of utilizing 
one wire from one side of a quadruplex or a duplex, to a branch ofiice. 

FIG. 188. 



^^ T ^-^.e, 




CARDANIER QUADRUPLEX — SHORT-WIRE REPEATER. 

It is, perhaps, more especially used for this purpose in emergencies, as when, for 
instance, one of the legs of a two- wire loop connection, from a duplex to a branch 
office, gets into trouble. In such a case, unless a repeating arrangement is put in at the 
main office, the perfect leg, and ,consequently, so far as the branch office is concern- 
ed, the entb-e duplex must remain idle until the defective leg is repaired. 

Since this emergency occurs quite often a diagram illustrating the arrangement 
may be of use. 

In Fig. 189 the necessary connections are shown. 

The defective short wire, in this case the receiving leg, is indicated as open, or 
" thrown out," at the 3-point switch, tp.' The dotted lines represent thy temporary 
wires used in making the connections. The sounder, s, may be cut out of tlie circuit, 
if desired, by connecting the temporary wire to the left hand screw post, instead of 
the right hand one, as indicated. The wire w' is disconnected from the pole- 
changer and is connected to the temporary wire leading to the post of repeating trans- 



QUADRUPLEX-SHORT WIRE REPEATERS. 



247 



mitter, rt. A wire is run also from the lever of rt to the rheostat, and thenoe 10 
ground, and the polar relay is given control of the repeating transmitter, rt, in the 
manner sliown. It will thus be seen that all the apparatus necessary to effect tnis 
temporary repeating arrangement is a spare single transmitter, five or six pieces of 
wire, and, for convenience in joining up, two thumb screws, and a rheostat. Some- 
times the rheostat is dispensed with and in that case the wire from the lever of rt is 

FIG. 189. 




MOFFAT TEMPORARY REPEATER FROM DUPLEX OR QUAD. TO BRANCH OFFICE. 

ran directly to ground. As this arrangement can be put into operation by an expert 
in one or two minutes its value, in point of time saved, is apparent. This expedient is 
due to Mr. J. M. Moffatt. When "ihe sending leg is in trouble the connections may 
be made as shown in Fig. 190. 

The connections in Figs. 189 and 190 are given on the assumption that the bat- 
tery wires, etc., are led to the various points ;.:signed. If not, it Avill be necessary to 
change the connections to suit each case, which is a simple matter when the general 
plan is understood. 



MULTIPLE QUADRUPLEX-SHORT WIRE REPEATERS. 

Sometimes it happens that wire facilities would be increased were it feasible to 
repeat from two or more quadruplex sets into the same branch office at an intermediate 
station ; or even to repeat from one side of a quad, "o two or more sides of differ- 
ent quads, at a main or repeating office. To make this remark clearer an instance 
that occurred in actual practice may be stated. Thtve were at Indianapolis, Ind., 
three quad sets — one to Chicago, one to St. Louis and one to Cincinnatti. It w:is 



248 



AMERICAN TELEGRAPHY. 



desired to give a lessee direct communication from Chicago to Indianapolis, St. Loais 
and Cincinnati, using for the purpose one side of each of the above mentioned quad 
circuits, and it was necessary that each of those offices should be able to communicate 
with each other, exactly as though all the offices were on a single wire. 

An arrangement devised by the writer to meet those requirements is to be seen in 
Fig. 191. All of the instruments and battery shown in the figure are supposed to be 
located in the main repeating office, except, of course, the loop, or branch wire, instru- 
ments at that point. 

FIG 190. 




The first sides of the quads are supposed to be used in this instance, consequently 
the pole-changers pc^, pc^, pc^, and polar relays pr^, pe,^ pr3^ ^^f ^]^q respective sets, 
only, are shown. In each case the polar relay controls a repeating transmitter rtS rt,^ 
KT^. In the figure, the polar relays being closed, the repeating transmitters are in the 
position indicated, and it will thus be seen that if the key at the branch office be 
operated, it will operate all of the pole-changers, since the loop or wire to the branch 
office passes also through the magnet of the pole-changers. On the other hand, should 
the operator, at Cincinnati for instance, desire to send to all of the other offices he 
may do so by operating his pole-changer which actuates pr^ at Indianapolis. In 
turn pr2 operates its repeating transmitter. This latter instrument, in opening, will 
open, at the point x, the circuit passing through pole -changer magnets pci and pc^ 
and to the branch office. The pole-changer pc^ of the Cincinnati set is not opened, 
however, as, at the moment the repeating transmitter rt starts to open, a local cir- 
cuit via the lever of rt^, including the local battery lb^, comes into play, and thus, 
automatically, keeps the magnet of pc^ closed. The local batteries lbS lb2, lr^ are 
arranged so that they coincide with and assist the loop, or single wire, battery, when 
this wire is closed. It will be seen by a casual observation that, in the same way, 



I 



249 




250 AMERICAN TELEGRAPHY. 

botli the Chicago and the St. Louis sets have, through their polar relays, similar con- 
trol of their respective repeating transmitters, and that each pole-changer is, at the 
proper time, kept closed, automatically, by its local battery, acting through the lever 
of its repeating transmitter. 

When it is not desired to use the quad sets as repeaters, the simple turnir.s* 
of the 3-point switches tp to the left will separate the sets, and the repeating trans 
mitters may then be used as sounders. It is plain that the number of quad sets 
brought together in this way is not limited to the number shown, and tliat more 
single wires could be looped in the series by the use of repeating relays, similar to r 
in Fig. 193 or 194, to operate the pole-changers or transmitters; it being understood 
that the introduction of single wires would unduly weaken the current so far as the 
operation of the local magnets of the pole-changers is concerned. Of course, the main 
and local batteries would have to be increased if additional wires were placed in cir- 
cuit. An advantage of this arrangement is that, when any one of the quadruplex or 
single wire circuits in the series is operated, every other circuit hears the signals and 
thus there is no "breaking " in upon each other, unintentionally. 



QUADRUPLEX-SlNGLE ^\"lRE AUTOMATIC REPEATERS. 

One of the important advantages of the quadruplex is the use to which it 
can be put between points where there is a scarcity of wires. For example. Between 
New York and Albany there is a large demand for wires. There exists beyond Al- 
bany a large number of medium sized towns and cities which do a fair amount of bus- 
iness with New York, sufficient to warrant the assignment of a wire between those 
points and the latter city. In order to meet the demand for facilities between the 
cities named, many of the wires between them are quadruplexed and one or 
both sides of the quadrujjlex are oj^erated into a single wire, or wires, west, north or 
east of Albany. To permit this, a repeating arrangement is necessary, as in the case 
of the combination of one side of a quadruplex and a branch or short wire, and, in 
fact, the main difference between them is, that, on the longer circuits, a relay has to be 
used to operate the pole-changer or single transmitter, as the case may be. 



THE EDWARDS SIXGLE WIRE -QUADRUPLEX REPEATING ARRANGEMENT. 

It is evident that, as in the quadruplex— short wire rej^eating arrangements, the 
one-half of any of the succes'sful repeaters is applicable to the single wire quadru- 
plex single wire repeating arrangements. In Fig. 192 the " Edwards " repeater is showiz 
adapted to this purj^ose. PC and pr are the pole-changer and polar rela}", respectively, 
of the first side of a quadruplex. rt is a repeating transmitter and R is a main line 
relay. The main line relay is used to operate the pole-changer, instead of having the 
main line pass directly through the magnet of the pole-changer, because of the 
large amount of current required to operate the latter instrument, namely, about one- 
quarter of an ampere, as against about four one-hundredths of an ampere; that is, 40 



QUADRUPLEX-SINGLE WIRE REPEATERS. 



251 



milliamperes, required by the Morse relay. The operation of this arrangement is as 
follows : 

The polar relay operates the repeating transmitter, which opens and ch)ses the 
single wire at x. This, of com-se, also operates the relay R in the single wire circuit, 
but the pole-changer is prevented from opening in response to the break of its local 
circuit at the contact point c of relay e, by the formation of an extra local circuit, 
I, 2, 3, 4, 5, 6, around the said contact points, via the lever of rt, at the moment when 
'the main line is opened at x. When the single wire is operated from an outside 
point the polar relay is not affected, and, consequently, rt remains closed. This leaves 
the extra local circuit i, 2, 3, 4, 5, 6 open at b. As the relay R is operated by the 
opening and closing of the single wire, consequently, the armature lever of that relay 

FIG. 192. 



% PC 




-^/wwwv 




Sf/z/^le nirc 



EDWARD'S QUADRUPLEX-SINGLE WIRE REPEATER. 

operates the pole- changer, by opening and closing its local circuit, in accordance with 
the signals transmitted. The 3 -point switch is used to cut off the relay r when the 
attendant at repeating station wishes to communicate with a distant end of the 
quadruplex circuit. 

THE WATERBURY QUADRUPLEX-SINGLE WIRE AUTOMATIC REPEATER. 

This arrangement, Fig. 193, like a number of other repeaters, goes by several dif- 
ferent names, one of which is the McPherson. 

It performs its alloted work in the following manner : 

As in the repeater just described, when the quadruplex is sending to the single wire, 
the polar relay pr operates the repeating transmitter rt. This operates the single 



252 



AMERICAN TELEGRAPHY. 



wire by opening and closing it at the point x of the transmitter. This cuts off and 
cuts in the main battery, mb. The smaller battery lb in the local circuit, formed 
by the wires i, 2 and the lever of et, keeps the relay closed during the time that 
ET is open. When the single wire sends to the quadruplex, the polar relay being closed, 
so is ET, and, hence, the circuit via wire i, 2 and the lever of rt, is open, and the 
relay r responds to the signals sent over the single wire, and its ar nature controlling 
the local circuit of the pole-changer, repeats the signals over the quadruplex circuit. 

This arrangement has the disadvantage, in stormy weather, that, owing to in- 
crease of current through the relay e, due to the escapes on the line, the tension on 

FIG. 193. 




T" 




/ir 



© 



m 



1 Q 



=D 



TF'\ 

9 W o 



MB 



WATERBURY REPEATER. 



the spring of its armature is so much increased that it is often beyond the current 
strength, due to the extra battery, lb, to keep the armature closed, when the polar 
relay opens. To remedy this the extra battery must be increased. Care should be 
taken to observe tliat this extra battery is connected up to coincide in polarity with 
the main battery, or a false signal will be occasioned. 



It is, of course, obvious that the occasions are rare when it will be desirable to 
repeat from a duplex into a single wire, inasmuch as the addition of the single wire 
to the duplex reduces the capacity of the duplex to that of a single wire. It is, how- 
ever, possible that occasions may arise when such a combination may be of use, as, 
for instance, when the business at a repeating office with the office at the other ter- 



WATERBURY QUADRUPLEX REPEATER. 



53 



minal of the duplex circuit may not be sufficient to warrant the assignment of a spec- 
ial wire between those offices. In that case it is practicable for the terminal stations 
cf the duplex to utilize the duplex during the time that the " single wire " station, or 
stations, may be sending to, or receiving from, the distant terminal station of the du- 
plex system. 

It is rendered practicable by turning the 3-point switch tp, Fig. 193, to the 
right, when the duplex is sending to the single wire, at which time the repeating sta- 
tion may "receive " from the distant duplex station, and by turning the 3-point switch 



FIG. 194. 



jBra/(rA Loop 




ARRANGEMENT FOR CONVERTING SHORT WIRE INTO MAIN LINE WIRE. 

TP' to the left, when the single wire is sending to the duplex, at which times the re- 
peating station may " send " to the distant duplex station. In the latter case the 3- 
point switch tp' cuts out the points of the repeating transmitter and, thereby, prevents 
the movement of the lever of that instrument from operating the single wire during 
the time that the latter is sending to the duplex station. In the former case the 3- 
point switch tp cuts out the contact points of the relay, with an analogous result. 

It is clear that the same device may be made use of in the case of the combina- 
tion of one side of a quadruplex and a single wire. As a matter of fact this device 
has been used repeatedly in the past to good advantage. One of the chief difficulties 
of the plan is that the operator at the intermediate station is apt to leave the 3-point 
switches out of position for the terminal stations. 

ARRANGEMENT FOR CONVERTING A SHORT WIRE INTO A " MAIN " LINE WIRE. 

It is, at times, desirable to put a number of branch offices on one branch circuit, 
or loop, in connection with a duplex or one side of a quadruplex. The writer has 
known as many as nine offices to be thus placed in connection with one side of a quad- 
ruplex. When the quad circuit is a long one and, especially if the No. 2 side is 
assigned for this purpose, much trouble is often experienced by the quadruplex attend- 



254 AMERICAN TELEGRAPHY. 

ants at repeating stations in keeping the instruments adjusted to suit the various 
styles of the different senders on the loop circuit. To remedy this difficulty, as far as 
possible, the arrangement shown in Fig. 194 was devised by the writer and was found 
of considerable utility in practice. The arrangement virtually consists in transform- 
ing the " loop " circuit into a main line by the addition of resistance furnished by tlie 
rheostat r'. The sounders in the branch office are replaced by relays, and the loop 
battery, in the main office, by a main battery mb, and, instead of running the loop cir- 
cuit through the coils of the pole-changer magnet, it is put through a relay, r, which 
latter is given control of pc, as in the figure. The automatic repeating arrangement 
employed is, virtually, the " Toye. '' The rheostat r', performs the double function of 
increasing the resistance of the loop and of keeping the relay r and, consequently, the 
pole-changer, closed, at the proper time. Should the number of relays in , the loop be 
excessive, it would be advisable to use two rheostats, to avoid too great a variation in 
the resistance due to the cutting out of the relays in the loop circuit when the repeat- 
ing transmitter is open, which variation might introduce a tendency to wavering in 
the repeating relay R. In the figure the apparatus is shown idle. 

HINTS ON THE MANAGEMENT OF QUADKUPLEX — SINGLE WIRE KEPEATEi:S. 

To properly attend to repeaters of any kind or any telegraph apparatus, a small 
thin file for cleaning contact points is indispensable. Files for this purpose are pro- 
curable from many of the larger electrical supply companies. The file should be 
about g^j inch thick, about \ inch wide, and from 2 to 2 J inches in length, and should 
be provided with an insulating handle. 

The attendant should see that all the contact points of the apparatus are in good 
order. Even if the dirt or oxide on a contact point has not become so thick as to be 
noticeable the circuit will, it may be taken for granted, work better without it. 

One of the most common sources of trouble on quad-single wire repeating arrange- 
ments is that due to imperfect connections at the points of the repeating transmitter, 
caused by dusty contacts. This prevents the extra local battery, or other device, 
from holding the pole-changer or single transmitter closed during the operation of the 
polar relay or neutral relay, and if the single wire repeating device is in operation at 
both ends of the quad circuit, the result is that the single wire is opened. If the 
repeating device is only at one terminal of the quadruplex circuit the end remote there- 
from gets his own writing back. 

Other causes which may produce the same symptoms are those due to a weak- 
ening of the extra local battery; (or, what amounts to the same thing, an excess ot 
strength of the '•' loop" battery and extra local combined, over that of the extra local 
alone), which may induce the attendant to increase the pull of the retractile spring 
of the quad pole-changer or transmitter when the branch office is sending; the con- 
sequence being that, when the polar relay operates the "repeating" trans- 
mitter, the pole changer also is operated, its strong retractile spring overcoming the 
pull of the magnetism developed by the extra " local " alone. This must be rem- 
edied by equalizing the strength of current passing through the pole-changer or 
transmitter in both positions of the repeating transmitter. 

Still another cause which may give the sending operator at the distant end of 



I 
I 

1 



HIGH POTENTIAL LEAK DUPLEX. 255 

a qnadruplex circuit his own writing back, is that of a stiff tongue on the 
quadruplex transmitter, combined with a weak extra local. This defect does not 
often occur, but it is sometimes puzzling when it does. The effect of such a com- 
bination is that the tongue of the transmitter will partly withdraw the armature 
from the magnet, until the tongue comes in contact with the bent-over end of 
the lever, when its power to further withdraw the lever will cease. This practically 
short-circuits the long end of the quadruplex battery, and thus by giving the 
operator at the sending end his own writing back, points to trouble in the points of 
the repeating transmitter. When the play is small on the quadruplex transmitter it 
is not at once detected that the lever is in motion. 

Direct Eepeating Eelats. — Of recent years the telegraph companies of this 
country have adopted on many of their long duplex circuits the direct polar relay 
arrangement, practically as described and illustrated in connection with the Wheat- 
stone duplex repeater, page 308, Fig. 232. In the Western Union arrangement, as 
devised by Mr. J. C. Barclay, an extra lever is added to the relay armature. 'To 
this lever is attached a contact point controlling a local sounder, by means of which 
the nature of passing signals may be read. In the Postal Telegraph-Cable Com- 
pany's arrangement of direct repeating relays for duplex circuits, the '^leak" relay, 
as used in the Wheatstone duplex repeater, is employed for the purpose of ascertain- 
ing the nature of the repeated signals. 

High Potential Leak Duplex. — When it is desired to operate a polar du- 
plex set from a high potential dynamo, as is sometimes the case, the general princi- 
ple of the Field dynamo key system for reducing the electromotive force at a given 
point maybe availed of. (See page 218, 2d paragraph, and page 223, 4th paragraph.) 
In practice on the lines of the Postal Telegraph-Cable Company the added resistance 
employed is 800 ohms, which with 800 ohms resistance at the dynamo machine (consult 
Figs. 176 and 179) equals 1600 ohms. The leak resistance L is 2200 ohms. Assuming- 
main line resistance ml and artifical line resistance al to be 2200 ohms each, the 
joint resistance of l, ml, al will be 733 ohms. Then calling the e.m.f. of dynamo 
machines 380 volts each, and with an added resistance of 800 ohms in circuit, the 
potential at J will be approximately 120 volts, for under these conditions the poten- 
tial at J will have dropped ||f| of 380 = 260, and 380 — 260=120 volts. With only 
800 ohms resistance in circuit the e.m.e. at J will be about 182 volts, since in that 
case the potential at J will have dropped Yii»ot 380=198, and 380 — 198 = 182 volts. 

In practice duplicate leaks and added resistances are interposed in the dynamo 
circuits between the dynamos and the contact points of the pole changer, instead of 
a single leak and added resistance as in the Field key system. A simple switching- 
arrangement is provided for cutting out the added resistances and leaks when it is 
required to employ the entire e.m.f. of the dynamos. 



CHAPTER XIV. 



BRANCH OFFICE SIGNALING DEVICES. 



m large cities where there are many branch offices, such as those of lessees of wires, 
etc., it is customary to "loop " in the branches from the main office; th^ charge and 
care of the line wire remaining in the hands of the main office. 

In order to enable the branch offices to report wire trouble promptly, it has been 
found advisable to supply each office with an auxiliary short wire on which to commu- 
nicate with the main office. The arrangement of the " short " wires has varied in dif- 
ferent cities. 

Several of these will be described presently, but the operation of a simple instru- 
ment used in connection therewith, namely, the buzzer, may first be explained. 

THE BUZZER OR INTERRUPTER. — This is an ingcuious device much employed to 
obtain a continuous vibration of the armature of an electro magnet, so long as j^ battery 
is permitted to act upon it. The principle of this arrangement is used in many systems 
of telegraphy. 

The manner of its operation is as follows: In Fig. 195 em is an electro magpet. a, 
is its armature, with contact on back stop. The front stop is insulated, b is a battery 

of any desired number of cells. The sprang, s, 
naturally draws the armature, a, against the 
contact point, cp. The moment this occurs em 
is magnetized, and attracts its armature. When 
this happens the circuit of b is broken, em is 
demagnetized, and the spring draws the arma- 
ture against its contact point again, thus 
closing the circuit. Again the em is magnet- 
ized, attracts its armature, again breaking the 
circuit with the former result, and in this way 
the armature is maintained in vibration, causing 
it to set up a hum, or buzz — hence the name 
of " buzzer." Usually there is a push button or 
other contact point at some part of the circuit 
which keeps it open excepting when the button is 
depressed. 

Very frequently the armature is apart of, or is attached to, a tuning fork, or reed, in 
which case a spring is not needed, as the resiliency of the reed causes its withdrawal 
when the electro-magnet demagnetizes. In Fig. 196 is given an illustration of a " tremb- 
ling" or " call " bell with buzzer connections. The armature, a, in this case, carries a 
flat, "tension" contact spring, which permits the retractile spring to be dispensed with. 

256 



FIG. 195. 



0- 



EM 




\^ 



CP 



~A 



s 



\ 



BRANCH OFFICE SIGNALING DEVICES. 



257 



It consists of an ordi- 

FIG. 196. 



NEW YOEK BRANCH OFFICE " CALL WIRE. 

A branch office call wire arrangement is shown in Fig. 197. 
nary metallic circ .it with the branch offices bo, cut in. 

A low resistance call bell, or buzzer, c b, ( in a local 
circuit in the main office mo,) is controlled by the back 
contact of the lever of the sounder s, and operated by the 
local battery b, so that when either of the branch offices 
opens the circuit to report trouble, or for any other 
reason, the ''buzzer" attracts the notice of the main office 
attendant. In the buzzer circuit is placed a key, k' which, 
when depressed, opens its circuit, thus enabling the at- 
tendant to clearly hear the inessage of the branch office. 

By having the key thus arranged the bell circuit is not 
so likely to be left inoperative as it might be if an 
ordinary closing key were used to open the local circuit 
temporarily . 

CHICAGO branch OFFICE SIGNAL ARRANGEMENT. 

This arrangement was used at one time in a Chicago 
main office, and is illustrated in Fig. 198. 

At the main office mo, k is a switch or key with upper 
and lower contacts. When on its upper contact the call 
bell CB is in circuit. Normally the keys in the branch offi- 
ces, BO, are open. When either of these keys is depressed the call bell, cb, is operated. 
The attendant at the main office hears the alarm and by depressing switch key k, he 

FIG. 197. 

MO 





BRANCH OFFICE SIGNALING CIRCUIT. 

opens the call bell circuit and throws his own sounder, s, and key, into cireuit,by means 
of which he then communicates with the branch office. This arruuoomeut has the ad- 



258 



AMERICAN TELEGRAPHY. 



vantage, if such it may be considered, that none but the main office can hear the re- 
marks of the respective branch offices. 



In the Western Union main office, New York, all of the single leased wire loops 
are brought into a spring-jack switch. Attendants at this switch are required to cut in 

FIG. 198. 




MO 



i 



BO 



I'l'I'I'I'H'h 



JBO 



CHICAGO" BRANCH OFFICE SIGNALING CIRCUIT. 



a relay into each circuit at regular intervals to listen to the working of the wire, thereby 
to anticipate a complaint or "call " on the part of the branch office or lessee. 

In addition to the foregoing measure to insure j^romptness in the detection of wire 
trouble, an alarm device is inserted in the branch office loop in the main office. 

This device, due to Mr. J. B. Hurd, is shown in Fig. 199. 



THE HUED BRANCH OFFICE CALL. 

The branch offices are " looped " as indicated in the figm-e. mb is main battery in 
main office, a is a "drop" indicator of two or tliree ohms resistance. R, is the Morse re- 
lay in branch office, s' is its sounder, s, is a 3-point switch, the switch ^, of which is 
connected to ground. Ordinarily, the current on the wire does not affect the drop indi- 
cator, A. When the branch office desires to attract the attention of the main office he 
throws switch ^ of s to the "ground " for a moment. This short-circuits the main bat- 
tery through the coil of the indicator, the result of which is that its armature is attracted, 
releasing the drop. The name or call of the branch office is written on the indicator so 



BRANCH OFFICE SIGNALING DEVICES. 



259 



that, at a glance, the main office attendant can see which circuit requires attention. 
This device saves the time that would otherwise be consumed in answering the branch 
ofi^ce to ascertain the identity of the caller. An electric bell is sometimes attached to 



Lifter 



JfairvQ^vce 



MB 



Ft^. »9<> 




JBram:^ Q/fcce^ 



Loop 




THE HURD BRANCH OFFIFE CELL. 



tlv^ drop to give an audible signal. By having the 3-point switch connected to both 
sMes of the relay the cutting out of that instrument is insured in the event of a trans- 
position of the sides of the loop in the main office. This device gives very satisfactory 
results. 



CHAPTER XV. 

LOOP SWITCHES. 

The chief use of a loop switch is to facilitate the '* switching " of loops and loop 
batteries, worked in connection with duplex and quadruplex sets. 

Although the term **loop " would signify an unbroken wire from the main office 
to the branch office and return, and was and is so employed in such cases, it has adhered 
to the two short wires, or " legs," now employed in connecting a main office with a 
branch office from a duplex or one side of a quadruplex set; which ''legs " are grounded 
at both the main and branch offices. 




LOOP SWITCH CONNECTIONS. 

In Fig. 200 a common form of loop switch and its connections are shown theorti- 
cally at l s. 

The wires, binding screws, plugs, or wedges, connections, etc., for one duplex or quad- 
ruplex ''loop," are outlined in the figure. The binding posts a, ^' and /, /' are 
placed on the back of the board at l s. The binding posts and the spring-jacks are con- 
nected, behind the board, by wires represented by the dotted lines. The spring-jacks c. 
c', project through to the front of the switch board, and are accessible for the insertion 
of the hollow plugs w' and w. These plugs, which are shown at their left ends in cross- 
section, in the figure, are of peculiar construction. They consist of an inner and an 
outer metallic tube, insulated from each other, as shown by the black line along a sec- 
tion of the tubes. The inner tube of each plug is connected to a small screw n', 2' ; 
the outer tube to the small screw n and 2. The small screws, n', 2', do not touch the 

260 



I.OOP SWITCHES. 



261 



outer tube, being insulated therefrom; nor do screws n, 2, come in contact witb the in- 
ner tube. Thus, when the plug is inserted in a spring-jack, the inner tube is connecter] 
with a pin at 7' or 3', and the outer tube with the spring at 7 or 3. The handles h, h' 
of the plugs are made of insulating material. 

The instruments to the right of the figure, at d s, are those of the No. 2 side of a 
quadruplex, ihe quadruplex main connections being omitted, t is the tranemitter. nr 




J 


A i 

1 M 






Ze^ 









POSTAL LOOP SWITCH. 



the neutral relay, r s the repeating sounder, etc. The tubes of w' are connected perma- 
nently to the wires running to the branch office. Wires leading from " loop" batteries 
b' and B are connected to the tubes of w. Wires leading from the 3-point switches s' 
S are connected to the binding posts a' a, respectively. 

By means of these devices if either or both of the batteries, b' or b, should fail, it 
is only necessary to remove plug w, from spring-jack c', and insert in the same spring- 
jack a plug connected with batteries known to be good. Or, if either of the '' legs " of 
the loop fail, it is only necessary to remove plug w' from spring-jack c', and insert in 
its place a "good" loop running to the same branch office. Or, if the duplex or quad- 
ruplex set fails, it is only requisite to withdraw plugs w, w', from the spring-jacks, and 
insert them in spring- jacks connected with a set known to be intact. The route of 
each circuitjfrom the battery at the main office to the earth at the branch office, may 
be readily traced on the diagram by means of the figures i, i'; 2, 2', etc. 

The loop batteries are, or should be, arranged iu a uniform manner so that every 



262 AMERICAN TELEGRAPHY. 

battery of the loop switch system may coincide as to polarity with the local batteries 
of the different duplex and quadruplex sets. Each plug and each spring- jack is usually 
marked with the number of the battery, or loop, etc. with which it is connected. 

When it is desired to cut off the loops from the duplex or " quad " sets it may be 
done by simply moving the 3-point switches at the desk, to the right. 

POSTAL LOOP SWITCH. 

The principle of this simple and efficient loop switch, for " gravity " battery cir- 
cuits, is shown in Fig. 201. 

Each duplex and quadruplex instrument is connected to a spring- jack and strap sj, 
sj', at the loop switch, l s, as in the figure, without the intervention of 3-point 
switches. 

If it is desired to repeat from one set into aftiother in the main office, it is only nec- 
essary to put in a double-cord and double-end wedge, such as do, in the spring-jacks; 
one wedge in each jack. 

For instance, acsuming t and p r to represent the transmitter and polar relay of 
two different '• quad " sets, if one wedge of dc be placed in s J, and the other in s j', PR 
will control t. 

To insert a "loop " wire in the local circuit of either the transmitter or polar re- 
lay, it is only necessary to put in a loop-wedge (as lw, at a,) in the spring-jack. If 
more battery be needed the battery wedge b w may be inserted with lw. 

To place a short leg of a loop in the circuits of t or pr, it is only needful to in- 
sert a leg-wedge, as shown at a. in the proper spring-jack. At a is also seen the man- 
ner in which two short ''legs," a "loop" wireLW, and battery wedge bw, may be 
placed in the circuit of a polar relay or transmitter. 

When it is found that the "loop " or "leg" batteries do not coincide with the 
"local " batteries the defect is remedied by simply reversing the position of the bat- 
tery wedge in the spring- jack. 

the DAVIS LOOP SWITCH. 

This arrangement, devised to faciliate loop and leg connections where the source 
of electromotive force is a dynamo, is outlined in Figs. 202 and 202 a. 

In Fig. 202 T is a transmitter of a quadruplex set and p' is a spring -jack con- 
nected with same, nk is the neutural relay of a quad set, with spring-jack p con- 
nected therewith, s is the reading sounder of the neutral relay, d, is the dynamo ma- 
chine assigned to local circuits and loops, s' and s are 3-point switches, one point of 
which is connected with the dynamo; the other point, viz a?, ;^;/ being connected to 
earth. These switches are usually turned to the right, thus connecting the transmitter, 
or the armature of the neutral relay, with the dymano. 

The brass plate upon which the jack rests, and which, in ordinary forms of 
spring-jacks, is in one piece, is in in the one used in the Davis arrangement,cut in two, 
as at p, p', and a resistance coil of 130 ohms is placed between the segments, as sliown. 

L, in Fig. 202, is a " leg " wedge. It has but one " live " face, that is, one metal 
face, the other side being insulated. The live face cuts out the 130 ohms when the 
wedge is inserted in the jack, as at p. 



LOOP SWITCHES. 



263 



fT\ 



The magnet coils of the pole-changers, transmitters, sounders, etc., are wound to 20 



otims. 



It will be seen, assuming the 3-point switches s s' to be turned to the right, that 

FlG. 202. 




FIG. 202 a. 



A 



^' 



i 



^^7: 



\FF 



DAVIS LOOP SWITCH. 

in the case of the apparatus at a, Fig. 202, the circuit has an added resistance of 160 
olims from d, while,in the case of the ai)paratus at b, the circuit lias an added resistance 
of 30 ohms, and also the resistance of a loop leg which is inserted by means of the 

wedge L. By withdrawing 
the wedge l the loop leg 
would be removed, and the 
neutral relay circuit would 
pass to earth in the main 
office, as at a, via the 130 
ohms. 

When it is desired to insert 
a loop or loops into the " re- 
peating " circuit, a double 
faced wedge, such as lw, is employed in the spring- jack. 

For repeating from one quad set to another, as from a to b, in Fig. 202, a double- 
end cord, having a full brass plate, r p, ^as in Fig. 202^) on one wedge, and a half plate 
H p, on the other wedge, is used; the full plate h p making contact, but leaving in the 
resistance ;^,as at p. In addition to the use of this double-end cord, either one of the 
3-point switches, must be turned to the left to complete the circuit and to avoid intro- 
ducing electromotive force at more than one point. 




CHAPTER XVL 



COMBINATION DUPLEX SYSTEMS, ETO. 



THE EDISON-SMITH DUPLEX. 



This duplex is arranged to operate with battery at one end only. It may be 
classed as a combination of the Stearns duplex and the polar duplex. Such a 
duplex is occasionally of utility when it is not feasible to place a battery at both 
terminal stations. 

The principle of the duplex is shown in Fig. 203. 

PC is a pole-changer, ne is a neutral relay, at station x. At station y, pr is a 
polar relay, and R is a rheostat; the latter capable of being short-circuited by the 
key K. 

FiG. 203. 





EDISON-SMITH DUPLEX. 

The neutral relay is placed in the circuit of battery b, within the contact points, 
c c oi the pole-changer, so that it is not affected by the" reversals '" of the battery, the 
direction of the current between those contacts being always the same. 

The relays nr, pr are wound " singly. " The rheostat e, at y, is so adjusted 
as to produce the variation in the strength of the current in the circuit necessary to 
operate the neutral relay at y when the key k is opened and closed, care being taken 
to leave sufficient current on the line to operate the polar relay when the resistance 

264 



THE MORRIS DUPLEX. 



265 



is included in the circuit. The polar relay pr is operated by the reversals of the 
battery due to the pole-changer at x, in the usual way. A repeating sounder ps may 
be used to offset any tendency to a "kick" in the neutral relay, due to the short- 
circuiting of battery b, at the moment of reversal. 



THE MORRIS DUPLEX. 



This duplex, due to Robert H. Mo'ris, illustrated in Fig. 204, is somewhat of an 
improvement on and modification of the Edison Smith duplex just described. It is mod- 
ified at station A to operate from two separate batteries or dynamo machines d d'. The 
neutral relay n s. at A is so wound that currents from either machine, although of op- 
posite polarity, pass around its core in the same direction and thus have the same 
magnetic effect upon the core ; hence there is no reversal of magnetism in that relay. 



FIG. 203a. 




THE MORRIS DUPLEX. 



At station B, the coils of the polarized relay pr are connected in series as shown, 
but are tapped in the middle iu such a manner that when the transmitter tr is closed 
the right-hand coil and the rheostat, r, are short circuited, leaving but one coil of the 
relay in operation. 



266 



AMERICAN TELEGRAPHY. 



The short circuiting of the rheostat and coil reduces the resistance of the circuit, 
thereby increasing the current and closing the neutral relay at A ; it being understood 
that the spring s of this relay is so adjusted as to withdraw the armature when the 
rheostat at B is in circuit, as in the Edison-Smith duplex. On the other hand, when 
transmitter tr at B is open both coils of pr, as well as the rheostat, are included in the 
circuit, and thus, while the current is reduced as desired to cause the opening of the 
neutral relay at A, the core of the polarized relay is magnetized to practically the 
same extent as when but one coil with the stronger current is in use ; this conducing, 
of course, to a more satisfactory operation of the relay. 

The local contact point of the neutral relay in this duplex is placed on the front 
stop to avoid the effect of the short circuiting of the dynamo machines at the contact 
poiats of the pole-changer at A, when the distant key is open. A continuity preserv- 
ing pole-changer is employed, this having been found more serviceable than the usual 
dynamo pole-changer. A repeating sounder, es, also with contact on front stop, may 
be used ad shown, to obviate aay static effects where the line is of sufficient length to 
warrant its employment. The polar relay is of course caused to operate a sounder in 
the usual way. 



FIG. ao4. 



A" 



^^ 



>r 



^ A 



^/^ =r 



() 



X 



-iiiiiiiNiiiiii 




SIEURS DIPLEX. 



THE SIEURS DIPLEX. 



By diplex transmission is meant the simultaneous transmission ot two messages 
in one direction over one wire. 

The Sieurs diplex system is entirely different in principle from the duplex sys- 
tems already described. The writer is not aware that it has ever been in continuous 
practical operation, but as it may be found of utility in some places, a description of 
it is here given. In Fig. 204 e is a reed, vibrating constantly while the diplex 



THE SIEURS DIPLEX. 266^ 

is iu operation, by the usual means, consisting of a local battery b^ electro-magnet m 
and the back contact shown. 

The free end of the rod r plays between two metallic strips f, f', which are given 
a tension towards the inner stops s\ s. The reed p is grounded at one end. The 
apparatus at a represents the sending station; that at b the receiving station. It 
will be seen that when the rod e is against the strip f, as in the figure, and when 
key, K, is closed, the positive pole of battery b is placed to the line. So long as the 
apparatus remains in this position, with key k' open, only momentary positive currents 
will pass to the line. Should key k' be closed, and key k open, it will be found that only 
negative pulsations reach the line. Should both keys be closed, momentary positive 
and negative pulsations will pass to the line. When both keys are open no current 
gets to line. 

At the receiving end b, p p' are polarized relays, which, it is known, will 
respond to either positive or negative polarities. In this diplex the armatures of 
those relays are provided with a light spring which causes the armatures to rest 
against the local contact points, <r, c, when both keys are open. The coils of the 
relays are so connected in the circuit that a current of a given direction will tend 
to move their armatures in a similar direction. It will be seen, however, that the 
local contact of each relay is on different sides. Each local circuit is furnished with 
a repeating sounder and a regular reading sounder. Thus, when the keys are open 
the reading sounder is open also, as in the case of the No. 2 sounder of the quad- 
ruplex when a repeating sounder is used. It is known that when rapid pulsations of 
electricity are sent over a circuit one instrument may be operated by them, while 
another instrument, not so sensitive, will not be visibly or audibly affected thereby. In 
the case in point either of the polarized relays may respond to pulsatory currents and 
may, by its armature lever, set up pulsatory currents in the local circuit which will 
not affect the repeating sounder ks, owing to the greater inertia of the armature of 
the sounder. 

Assume that positive currents deflect the armatures of the relays, as shown, and 
that relay p' is responsive to key k; relay p to key k'. 

In the figure, when K is closed positive pulsations are sent over the line, the 
effect of which is to aid the spring of p' to hold the armature against c' ; the effect on 
p is to send its armature over to its back stop, away from r, but as the current is only 
momentary the spring tends to withdraw the armature to its contact point, and, as 
long as the positive pulsations continue the armature is kept in a state of rapid vibra- 
tion, sufficient to open the local circuit of the lepeating sounder, Rs, which, it is seen, 
closes the reading sounder, s, thereby effecting the desired result of closing that 
sounder when key k is closed. If key k be open and key k', closed, negative pul- 
sations are transmitted, the effect of which, on relay p, is to assist its spring in hold- 
ing the armature against its contact point c. But its effect on the armature relay p' 
is to put it in a state of vibration, which also opens the local circuit of es', and 
thereby closes the reading sounder s' in the usiuil way. When both keys are closed, 
together, rapid alternations of positive and negative pohirity ensue with the result that 
both relays are rapidly vibrated, thereby opening both repeating sounders and closing 
both the readins: sounders. 



266^ AMERICAN TELEGRAPHY. 

This arrangement might be mtodified to dispense with the repeatina: sounders 
but the latter assist in making a more perfect signal than would be obtained without 
themo 



CHAPTER XVII. 
SUBMARINE TELEGRAPHY. 

SIPHON RECORDERS — STEARNS DUPLEX — MUIRHEAD DUPLEX, ETC. 

When the first Atlantic cable was laid the ordinary Morse method of tele- 
graphing was employed, but it was soon discovered that the strength of current 
necessary to secure the operation of the Morse receiving apparatus tended to reduce 
the speed of signaling to a very low rate; namely, one or two words per minute. 

The cause of this slow signaling may be illustrated by analogy: 

Suppose a long, large pipe to extend from a to b, with a pump at the near end A, 
to drive water through the pipe, and a wheel at the distant end, b. Assume that it is 
intended to transmit signals by causing the wheel to turn out of a certain position when 
the water is flowing, and to resume a normal position by the pull of a spring or 
weight when the water ceases to flow. It is evident that if a cumbersome wheel is 
employed a larger volume of water must pass through the pipe to turn it, and this 
volume of water will require more time to flow in and out of the pipe, than if a small, 
light wheel should be employed, since the latter will respond to a much less volume of 
water, and thus may be operated more rapidly than the much larger wheel could be; 
in fact, by a volume of water so small that it would have no perceptible effect on the 
larger wheel. 

In the case of a long submarine cable the employment of apparatus requiring con- 
siderable strength of current for its satisfactory operation is, perhaps, relatively, more 
detrimental than would be the employment of cumbersome apparatus in the case of the 
water-wheel analogy, for the reason that, owing to its static capacity, when such a 
cable is conne<;ted with a battery the charge at first arriving at the distant end is very 
small and only rises to its maximum, gradually, and, when the cable is disconnected from 
the battery the discharge is, approximately, as gradual as the charge; the static 
capacity, as it were, retarding the passage of the current to remoter parts of the con- 
ductor until the nearer portions have received their respective static charges. It is, it 
may be said, virtually, as if, in the case of the water-pipe analogy, small closed pipes 
should be run off from the sides of the main pipe, the filling, or charging and discharg- 
ing of which, it is evident, would retard the arrival of the full volume of current at the 
distant end, and would also prolong the time of discharge of the pipe to a greater de- 
gree than would be the case were the small, lateral pipes absent. 

It will be obvious, on consideration, that the static capacity of a long submarine 
cable, (as compared with an overhead wire of equal length) will be large, because of 
the nearness of its conductor to the earth throughout, and the high specific inductive 
capacity of its insulating medium, usually gutta-percha, both of which tend to increase 

267 



268 



AMERICAN TELEGRAPHY. 



the total capacity of the cable and thus cause it, with a given electromotive force, to 
take a greater static charge than would be the case if, for instance, the conductor pos- 
sessed resistance alone, or resistance with but a small capacity. {See Static Charge of 
Conductors), From the foregoing it is clear that a desideratum in submarine tele- 
graphy is a receiving instrument which shall respon i to very feeble currents, since the 
feebler the current required the shorter will be the time of charging and, consequently, 
discharging the cable, and, hence, the more rapid the signaling. 

MIRROR RECEIVER. 

The receiving instrument iirst successfully employed on long submarine cables 
\vas the Thomson reflecting galvanometer, an instrument which, as already stated, can 

FIG. 205. 




THOMSON SIPHON RECORDER. 



be made responsive to very feeble currents. In the operation of this method the gal- 
vanometer is placed in the circuit of the cable and hence is responsive to signals trans- 
mitted over that circuit. The spot of light reflected from the mirror is thrown on a 
screen in a darkened room. The ''International" code is employed. The dot and 
dash are distinguished from each other, not by the duration of the signal, but by the 
direction of the deflection of the spot of light on the screen. For instance, an imag- 
inary zero being at any given point on the screen, a deflection of the spot to the left of 
the zero represents a dot, one to the right of the zero, a dash. The advantage of dis- 
pensing with the Morse " dash " is that it avoids filling up the line with a prolonged 
charge, and thus permits speedier signaling. The direction of the deflection dependj* 



THOMSON SIPHON RECORDER. 269 

on the direction in which the currents pass tlirough the galvanometer, and this is regu- 
hited by a reversing key or "tapper " k , shown at the left of Fig. 205, at the sending 
station, which sends a positive or negative current to the cable as one or other of the 
single keys, k or k\ of the reversing key, is depressed. 

At rest, keys k k' press up against the brass strip b. When either key is depress- 
ed it leaves the strip b and makes contact with the lower strip x. The poles of cable 
battery cb are connected to strips ^ and jic-, as shown. 

Assuming that a positive pole of the battery deflects the " spot " to the left, and that 
a negative current deflects it to the right, the letter a would be formed by depressing, 
first the key k^ placing the positive pole to the cable; and then the key k\, placing the 
negative pole to the cable. The letter s would be signaled by three consecutive de- 
pressions of key k. 

It is seen that every time both keys, k k\ touch the strip b the cable is placed to 
the earth direct, thus discharging the cable, more or less, between each signal. It is 
this partial discharge between each depression of the same key which causes the suc- 
cessive deflections on a given side of zero. 

In the reception of signals by the foregoing method, two clerks are required ; one 
to read out the letters or words as received, the other to write them down. Thus no 
automatic record of the signals is made. This defect was supplied by a subsequent 
invention of Sir Wm. Thomson's; namely, the siphon recorder, which is outlined in 
Fig. 205. 



THE THOMSON SIPHON RECORDER. 1 

In the operation of the siphon recorder advantage is taken of the fact that, when 
a current flows in a wire the vicinity of the wire becomes magnetic, the magnetic effect 
thus set up being at a right angle to the length of the wire. This is shown by the 
action of a magnetic needle, which, when freely suspended over such a wire will tend 
to place itself at right angles to the wire; or if, on the contrary, the magnetic needle 
be rigidly held while the wire is freely pivoted, the latter will tend to place itself at 
right angles to the needle. The magnetism thus developed in the vicinity of the wire 
will be north or south magnetism (or in a positive or negative direction), depending 
on the direction of the current traversing the wire; and thus, if the direction of the 
current be changed at intervals, it will cause an oscillation of the wire suspended under 
the needle or other magnet. 

In Fig. 205 an oblong coil of fine wire a is suspended, by a silk fibre f, between the 
poles N s of a powerful magnet, in such a manner that, when a current passes through 
the coil the latter tends to place itself at right angles to the poles of the magnet. In 
other words, the coil becomes, for the time being, a magnet, with the equivalent 
of north and south poles, which change from side to side of the coil in accordance with 
changes in the direction of the current passing in it, with the result that its poles are 
alternately attracted or repelled by the poles of the permanent magnet, between which 
the coil is placed.* Or, if the strength of current in the coil be varied, its direction re- 
maining uniform, the magnetic strength of the coil will vary also, allowing the coil to 

* The coil is normally brought to and held at zero by means of the two small weights W, Fig. 205, which move up an<i 
down in grooves on the inclined plane; being suspended as shown from the coil by silk flbre. The weight* do not niucli 
exceed one ounce. 



270 AMERICAN TELEGRAPHY. 

advance or fall back, slightly, between each variation of current strength ; thus giving 
the coil an oscillatory motion. 

Another way of considering the immediately foregoing is to assume that the 
action of the magnetic needle is due to the tendency of magnetic lines of force to co- 
incide in direction. Thus, as the lines emanating from the wire are at right angles to 
it, it is natural that the needle should tend to set itself at right angles to the wire, 
since^ in that position, the lines of force of the needle will coincide with those of the 
wire magnet. Similarly, in the case of the magnet n. s. the lines of force pass from 
the north to the south poles, and hence are at right angles to those of the coil ; conse- 
quently, in the effort, so to speak, of the '' lines " to coincide in direction, the coil is 
deflected, as intimated. A piece of soft iron, i, is placed within the coil to concentrate 
the lines of force and " direct" them across the coil. 

A siphon, d, consisting of a very small glass tube, is attached to the coil A by a fine, 
but rigid wire r. The siphon is so suspended as to be free to move in unison with the 
coil. The lower and bent end of the siplion is placed directly over the centre, or 
imaginary zero, line of a paper ribbon p. The end of the siphon remote from the paper 
dips in an ink well b, and, by means of an electric machine, termed a " mouse-mill," 
M M, outlined in the figure, very fine dots of ink are deposited or projected on the paper 
tape. The mouse-mill is driven by a suitable motor not shown. 

There are two explanations as to the exact manner in which the ink is placed on 
the tape. One is that the electricity developed by the mouse-mill causes the ink 
to be spurted in minute drops across the air space between the end of the siphon and 
the paper. The other, due to Cuttriss, is that a static charge of electricity generated 
by the mouse-mill is collected at the end of the siphon ; that this charge tends to unite 
with '* opposite " electricity accumulated on the paper tape p, behind which, at that point, 
is a ground plate. The siphon is thereby attracted towards the paper, and, as the latter 
is kept in a slightly humid condition, the moment the ink on the point of the siphon 
touches the paper the charge of electricity escapes, whereupon the siphon returns to its 
normal position ; but in an instant the charge is renewed, the siphon is again attracted 
to the paper, and in this way it is maintained in vibration at its fundamental rate. 
The amount of charge is regulated, as desired, by the insertion of a small 
piece of moist thread w' in the mouse-mill circuit. The siphon does not impinge on 
the paper and thus friction is avoided. 

A reversing-key, k, similar to that used in the mirror system, is used in transmit- 
ting signals, and the momentary pulsations of positive and negative currents through 
the coil cause the lower end of the siphon to move to one side or the ether of the zero 
line of the paper tape, thus leaving a zig-zag series of marks on the paper, readily 
recognized as dots and dashes by the cable operator. In this way the signals are re- 
corded as received. Further reference to the siphon will be made shortly. 

THE CUTTRISS MAGNETIC KECORDEK. 

The operation of the Thomson siphon recorder is sometimes delayed by the fail- 
ure of the ink to flow, or by a failure of the siphon to vibrate to and from the paper 
tape. This is generally due to an accumulation of moisture on the mouse- mill or ink- 
well supports, which permits the charge to escape without passing through the siphon. 



CUTTRISS MAGNETIC RECORDER. 



271 



Some <lifficultY is also, at times, experienced in maintaining the paper tape in a proper 
degree of liumidity. 

Cuttriss sought to overcome these difficulties by the arrangement shown, theoret- 
ically, in Fig. 206. 

In this arrangement, coil a; permanent magnets v, s ; soft iron i' within tlie coil; 
an ink-Avell i, and siphon s, are used as in the Thomson siphon recorder. The mouse- 

FIG. 206. 




CUTTRISS MAGNETIC SIPHON RECORDER. 



mill, is, however, dispensed with. The coil is pivoted on line, agate bearings, and it is 
brought to a zero by the use of delicate springs k, k'. The siphon consists of a glass 
tube about one hundredth of an inch in outside diameter; the diameter of its ap- 
erture being about five one thousandths of an inch. On its lower end a very small 
piece of soft iron t, about one-eight of an inch in length, is placed. This iron tip is 
placed close to the paper tape, p, but does not touch it. The paper at this point is 
caused to pass over a magnetic "table" m, which is magnetized by contact M'ith the core 
of an electro-magnet, e m. Magnetic vibrations are set up in the" table," by means 
of the vibrating rod, or reed, r, which so acts as to cut the resistance r in and out of 
the local circuit of battery b. This increases and decreases the current in the circuit 



272 



AMERICAN TELEGRAPHY. 



of EM, and thus varies its magnetism. The resistance of r may be increased until the 
strength of current in the circuit is practically nil, and until the effect is as if the circuit 
were^ " broken " while that resistance is in; the presence of r, however, diminishes 
sparking at the contact points c' of R. This momentary magnetism of e m tends to at- 
tract the iron t on the siphon, and, if the rate of the magnetic vibrations of e m corre- 
sponds with the fundamental rate of vibration of the siphon, the latter will vibrate m 
unison with the vibration of the rod r; otherwise it will not. 

In order to secure a rate of magnetic pulsations in the electro-magnet e m corre- 
sponding to the fundamental rate of vibration of the siphon, the vibrating rod k is 

FIG. 207. 




CUTTRISS MAGNETIC KECORDER. 

made to carry a glass tube g, partly filled with mercury. The tube is attached to the 
steel rod as shown. At its upper end e carries the armature of the electro-magnet, m'. 
When the tube is set in vibration, it will continue to vibrate in the well- known 
way common to circuits connected up in the manner shown in the figure— which will 
be recognized as virtually the manner in which " buzzers " are connected. But the rate 
of vibration of the rod r may be varied by raising or lowering the column of mercury 
contained in g, and this is readily done by means of rubber tube r' connecting the 
glass tube with a reservoir x in which mercury is held. By adjusting the amount 
of mercury in the tube by means of the plunger p inserted in the reservoir x, a point is 
reached where the vibrating rate of the tube coincides with the natural rate of vibra- 
tion of the siphon. 

When this result has been secured it is indicated by the appearence of a fine ime 
of dots on the moving p^per tape, and signals are received by marks to the right and 
left of zero as in the 'case of the Thomson siphon recorder. 



CUTTRISS MAGNETIC RECORDER. 273 

The siplion is attached by wax to the cradle c, which is com- 
posed of a light metal. The cradle is delicate!}^ suspended as indicated 
iQ I in the figure. A fine wire, or fibre r, reaches from the cradle to a 
, pin projecting from the top of the coil a. A fibre from a extends to a 
Kf very sensitive flat spring k'. Another fibre extends at a right angle 
""*( tor. One end of this fibre is attached to a fine, flat spring k ; 
the other end is rigidly held by an adjusting screw a. The springs 
K, k' are adjustable by the indices /', /'. By this arrangement of 
---' fibres and springs it will be seen that any tendency of the coil a to 
1^ : place itself at a right angle to the permanent magnets will deflect 
the siphon to the right or left, as the case may be, of the imaginary 
___' zero. The Cuttriss recorder, as it appears in practice, is shown in 
'^ I Pig. 207. The permanent magnet is of nearly circular form. The 
^ , letters in Fig. 207 refer to parts similarly lettered in Fig. 206. In 

J the latest form of the Cuttriss recorder a small, curved iron cheek, 

^ I movable in a groove, is placed on the top of the permanent mag- 
~~"j nets, one on each pole. These nearly embrace the upper part of the 
^j coil. A small iron pin is attached to the upper end of the coil. A 
; slio^ht movement of the movable cheeks assists in adiustinsj the 
^! position of the coil in the field and permits the removal of one 

I of the adjusting springs alluded to. The presence of the iron in ^'^ ^ 
_-.' ihe coil affords a means whereby the attraction of the permanent 
5^ I magnet tends to, measurably, uphold the coil, thereby removing nearly 
g I all friction from the agate bearing; in fact the coil is, as it were, 
— - " floated " between the mao^nets. 



An important advantage accompanying the siphon recorder and ^^^^ 
'w j mirror metliods of signaling is that a "variable" zero is not an obstacle ^-n^ 

to their successful operation. By that is meant that it is not essential ~"^ 
•"^ : that the "spot," in the mirror method, or the siphon, in the recorder 
arrangement, should come back to a stated zero between each pul- 
sation. To indicate that the signals are either dots or dashes it is 
sufficient that one defltction should go, or "climb," beyond the <—> Sv 
I other, in one direction, with but a slight fall between each character. 
^ j A change in the character of the signal from a dot to a dash, or vioe ^~^^ 
versa, is indicated by a more pronounced fall or rise beyond a 
preceding " peak " or valley. In Fig. 208 is shown a specimen of ^ n" 
"^ j signals as received over a 1,000 mile section of an Atlantic cable by 
a Cuttriss recorder. The characters, as indicated by. the underlinino% 
\ ^ j represent the " International '' alphabet. It may be seen that what 
r — ', would be an intermediate line between the dots and dashes, or the c^ , ^ 
>*^ i upper and lower peaks, varies considerably from a straight line. The 
')~^ \ same characters as they might be received on a very short circuit are 

" , 5> shown in Fig. 208^. ,,,^ ^^,. ^ 

^ Y> ==> t IG. 200 a. 



2/4 



AMEklCAS TELEGRAPHY. 



EAETH CURRENTS. 

"WTien the terminals of a long cable are placed directly in the earth it is found 
that, so-called, earth currents; of sufficient strength to operate the sensitive receiving in- 
struments used on such cables, are almost always observable. At least two causes have 
been assigned to explain these currents. One is that they are due to a difference of 
electric potentials of the earth at the terminals of the cable; tlie other is that the 
currents are due to variations in the density of the earth's magnetic lines of force, 

FIG. 209. 



/JOOO 




CABLE TERMINAL CONNECTIONS — SIMPLEX WORKING. 

which in "rising'' and " falling/' "cut " the conductor of the cable. Probably these 
currents are due to both causes, but for the present purpose it will suffice to consider 
them as only due to the former cause. 

Ordinarily, these earth currents are neither very powerful nor very variable. 
During the prevalence of violent "magnetic" storms, however, they are very marked, 
so much so. indeed, as not only to disturb the sensitive cable apparatus but also the 
much less sensitive Morse apparatus on land lines. 

It is, of course, essential that means should be adopted to avoid or minimize the 
effects of these earth currents in submarine telegraphy. 

It is known that when the terminals of a condenser^ of superior construction, are 
oppositely electrified, as by the attachment of a battery to one of the terminals, while 
the other terminal is grounded; or, by placing one pole of a battery to one terminal 



SIMPLEX CABLE WORKING. . 275 

and the other pole to the other terminal of the condenser, a current of momentary 
duration occurs in the wires leading to these terminals, after which, so long as a 
uniform difference of potentials is maintained, at the terminals, there will be no fur- 
ther indication of current in the connecting wires. Advantage is taken of this fact, 
in submarine cable telegraphy, to nullify the effects of earth currents, and, to that 
end, condensers are interposed between the terminals of the cable, and the battery or 
the earth, as, for instance, is shown at c' in Fig. 209. The capacity of the condenseis 
thus used is varied with the requirements. Those employed on the Atlantic cable 
have a capacity of about 50 microfarads. 

Inasmuch as the capacity of a condenser is, generally speaking, proportional to 
the number of its plates in service, and as its " charge," with a given difference of 
potentials at its terminals, decreases as the plates are diminished in number or size, 
it is clear that a tendency t :> an increase in the strength of the earth currents could 
be offset by a reduction in the capacity of the interposed condenser. This princi- 
ple, it may be remarked, has been availed of frequently by the writer and others in 
experimental and regular work in connection with simultaneous telegraphy and tele- 
phony, and in other somewhat similar systems, in which sensitive apparatus, such as a 
telephone receiver, is used to receive "pulsatory" signals, and in which the pulsatory 
system is "separated" from the main line, by condensers. In those cases the capacity 
of the condenser is adjusted until the noises in the telephone, due to "induction" from 
parallel circuits, are silenced or, at least, rendered ''harmless," when, if necessary, 
the pulsatory signaling currents are increased in strength by an increased e. m. f., 
to compensate for the diminished capacity of the condenser. 

Assuming a practically constant difference of potentials at the terminals 
of a cable, it follows that, if a condenser be interposed in the circuit, no 
current, or, at most, a gradual rise or fall in its strength, such as would produce a 
large curved zero line on the paper strip, will be manifest in the receiving apparatus 
due to the electric potential of the earth, after the first momentary charge. This leaves 
the cable free to be charged by comparatively rapid variations in the charge of the 
condenser, which variations are set up by the battery and transmitting apparatus at 
the cable terminals. 

It will be observed that the cable and condenser, Fig. 209, are virtually connect- 
ed in " series, '' the conductor of the cable being one plate of an extensive condenser. 
Hen'3e, as the " charge " is proportional ( See Condenser ) to the capacity, and as 
the total capacity of the cable and condenser is less than the condenser would be 
alone if its other terminal were connected directly to earth, a higher electromotive force 
is necessary for the transmission of signals when the interposed condensers are em- 
ployed than if the battery were connected directly to the cable; the difference, in 
practice, being roughly, about as 3 to i . The electromotive force employed on the 
Atlantic cables is about 30 volts, in duplex working., The " Fuller" battery is fre- 
quently used. 

Another important advantage in using the interposed condenser is that, owing to 
tlie quick charge and discharge of the condenser, as compared with that of the cable 
when connected directly to the battery, the signals are much more clearly deiined. 



276 AMERICAN TELEGRAPHY. 

the deflections of the mirror and the of recorder coil being much more sharply cur- 
tailed. 

SIMPLEX CABLE TELEGRAPHY. 

Long submarine cables are worked both singly, or " simplex," as it is termed, and 
duplex. In either case currents of both polarities are employed in the transmission of 
signals. 

One terminal of a cable with apparatus arranged for simplex working is shown 
also in E ig. 209. In this figure k is a double, or reversing key, similar to that shown 
in Fig. 205, in connection with which its function is explained, s is a switch which 
is used in changing from "sending " to "receiving," and vice versa The metal strip 
s', is pivoted on insulated block a'^. There is a contact segment on ^.and three simi- 
lar contacts on a-. The upper segment on ^^ is connected to key iv at k'. The 
two lower contacts on a-, to earth. The contact on a is connected by a wire with a 
switch ES. The block a^ is connected by wire to switch rs'. e is the " recorder " or 
" mirror " galvanometer, c' is the interposed condenser of large capacity, c is the 
cable. 

When the switch s is set for "sending," as in Fig. 209, it may be seen that there 
is a direct route to the condenser and cable, via wires w w, for the sending current; 
but, if it is desired to observe the manner in which the signals are being transmitted 
a portion of the sending current may be diverted through the recorder, via wire w', w\, 
by means of the switch rs'; the amount being regulated by the low resistance coils 
r' r' r' . 

In some stations a large resistance, approximating to that of the cable, say, 
about 15,000 ohms, is so placed as to be readily attachable by a suitable "strap" to 
the switch rs. When thus connected the current from battery b divides between the 
cable and the high resistance, and, assuming the short-circuit coil o in es' to be used, 
the terminals of the recorder r would be, practically, at equal potentii;ls, so that no 
current would flow in it, but by the introduction of a resistance at es' a small por- 
tion of the current from the home battery is diverted through the recorder. When 
the high resistance is used a resistance of 53 ohms inserted at es' has been found to 
give satisfactory results. 

When the apparatus is to be arranged for "receiving," the handle of lever s' of 
switch s is raised, by which act contact is broken between s' and the contact on a. 
Hence the " received " current is caused to pass through the recorder, thence to the 
middle block a^ of s and to the earth, via a^ . The full, received current may be caus- 
ed to pass through the recorder or mirror coil by turning the strap h of es to the 
vacant button at the left. The resistance coils in rs are employed to diminish the 
deflections of the receiving instrument should the " received " current, passing through 
the recorder, be too strong. 

When " electrified " ink is used and when a tendency to^ lateral vibrations exists. 
it has been found in practice that the3,ooo-ohm shunt in RS sometimes exercises a 
steadying effect upon the siphon. These lateral vibrations are noticeable when the 
paper is not sufficiently humid ; they are assumed to be due to the attraction of the 
«j\eotritied siphon by the metallic sides of the paper guide. 



CABLE DUPLEX WORKING. 



277 



In order to discharge the cable before the switch s is set for receiving, thereby 
to prevent possible injury to the recorder, the metal contact on block a^ switch s, is 
slightly extended, so that the strip s' makes connection with the contact 2 on a"^ , for 
8 a instant, before connecting with contact 3. 

DUPLEX WORKING. 

When the cable is worked "duplex, " theswitchs is not used, as the effect of the 
inrush and outrush of current due to the charge and discharge of the cable, upon the 
" home" receiving instrument,is avoided by placing it in the bridge wire of a Wheat- 
stone bridge; that method of rendering the home apparatus practically irresponsive 
to the operation of the home battery keys being the one most generally used in snb- 
marine duplex telegraphy. 

The " artificial,'' or " false " cable corresponds to the " artificial " line in over 




THEORY— STEARNS ARTIFICIAL CABLE. 



land duplex telegraphy, but it is required to resemble the cable proper much more 
exactly, as regards resistance and static capacity, than does the artificial line in over- 
land telegraphy. 

The reasons for this are that in the case of the overland conductor the capacity 
is much less, and the insulation resistance is, generally speaking, much inferior, to 
that of a cable. Thus, in overland telegraphy, there are numerous external points at 
which the static discharge may escape, thus diminishing the amount that reaches the 
receiving station. 



It has been found that the artificial cable must especially resemble the cable 
proper, the first few miles of its length. 

There are two forms of artificial cables in practical operation in submarine du- 
plex telegraphy, namely: the " Stearns, 



Stearns artificial cable. — In Fiir. 



or " Varley,'' and the " Muirhead. ' 

210 Stearns artificial cable is shown in 



278 



AMERICAN TELEGRAPHY. 



theory. This artificial cable consists of a series of resistance coils, k, r etc., to 
which condensers are attached at x^ x, etc., as shown in the figure. 

In practice the " artificial " cable is put up in large boxes and the terminals of 
the resistance coils are brought to the outside of the boxes. The terminals of the 
condensers are also made accessible, outside of the boxes, by flexible cords, to which 
are attached suitable plugs, and by means of which condensers may be added to the 
resistance coils to give them " capacity," until a " balance " is obtained, which will be 



0^ 



^ 





2000 0/(jns 


^-^ 


% 111^ 


Vs 


^^efiS^WWVs^ ^ 




li 


J/' 


A 


^ 


rrmt 



CccSle- 



% 



ZOOO O/t/ns 




c 






H'l'l'I'H 




CABLE duplex; STEARNS ARTIFICIAL CABLE. 

when the artificial cable is equal in resistance and capacity to the " real " cable. 

Stearns CABLE DUPLEX. — A diagram is .given, in Fig. 211, of a long submarine 
cable as arranged for duplex working with the Stearns artificial cable, at one end. 

The transmitting and receiving instruments are the same as those employed in 
simplex working. The method employed to ])revent the interruption of received 
signals by the home transmitter is that of the Wheatstone bridge, b' is a box con- 
taining the arms a, b, of the *' bridge, " consisting of abouti,ooo ohms, each. The 
ends of the arms a a, are connected to split discs, as shown, into which metal 
plugs are inserted for duplex working. This arrangement is provided to facilitate 
changing f.om " simplex to '' duplex," and vice versa; the removal of the plugs dis- 
connecting the recorder from the bridge arms. Condenser c, and the recorder or 
mirror, r, are in the bridge wire, ac are boxes containing the Stearns artificial 
cable. BR is a rheostat composed of about 40 small coils of wire, in series, each 



MUTRHEAD CABLE DUPLEX. 



i79 



coil, J ohm : the terminals <?, e' of the series are connected, as indicated, to the arms a, b 
of the bridge; the metal arm m is connected to a wire leading to the condenser c'. 
By moving the arm m around on the metal pins p, p, etc., resistance may be added to 
and taken from one or other of the bridge arms to complete the balance. 

MuiKHEAD ARTIFICIAL CABLE. — The Muirhcad artificial cable is shown theoreti- 
cally in Fig 2 1?. The object of this form is to make the artificial cable correspond 
exactly with the actual cable, both as to resistance and capacity, mile, per mile, of each. 
Tliis is practically accomplished by using continuous strips of tin-foil, cut in ribbons 
:)f various widths, which are placed in proximity to, but separated from, other strips 
of tin-foil, which latter are, or may be, connected to the earth, at will. The tin-foil 
ribbon thus arranged is enclosed in a box with accessible terminals on the outside of 
the cover, virtually as indicated in the figure. The terminals x are those of the tin- 
foil strips E,used as a resistance ; terminals x' are those of the tin-foil strips c adapt- 



er X 



FIG. 212. 
X X 



/? 



wm 



/I 



B 



ii'X' iiX' Q^' 

THEORY MUIRHEAD ARTIFICIAL CABLE. 



bx' 



ed to add capacity to the strips c when terminals x' are connected with " ground. " As 
many boxes are added as may be required to equal the entire cable in both of said 
respects. 

MuiRHEAD CABLE DUPLEX. — The councctions and arrangement of apparatus now 
employed in duplex working on many of the longest submarine cables is shown theo- 
retically in Fig. 213. 

Tlie transmitting keys k are the same as those used in simplex cable working. 
BR is the rheostat of small resistance bobbins used in procuring a " fine " balance on 
the cable, c, c' are condensers, placed in the bridge arms in place of the usual re- 
sistances. R is the receiving instrument, in the bridge wire, ac is a Muirhead artifi- 
cial cable. The capacity of the condensers, c, (> is about 50 microfarads each; th?.t 
of the small condenser c^, about 3 to 5 microfarads, sub-divided into fractions of 
microfarads. The bridge wire condenser c^ has a capacity of about 50 microfarads. 

This arrangement of the condenser in the arms of the bridge, in place of resist- 
ances, is termed the Muirhead "double-block." It is said to increase the signaling 
capacity of the duplex about 15 per cent. The average rate of signaling on long sub- 
marine cables is about 25 words per minute in either direction. 

The arrangement of resistances between the " earth " plates, or foil, of the artificial 
cable, and the earth, is varied, both as to amount and as to location on the artificial 
cable, on different cables, but that shown in Fig. 213 may be considered as practically 
representative. R'is a small resistance intended to balance the wire leading from the 
cable office to the terminal of the cable; it may consist of but a few ohms. A short 



28o 



AMERICAN TELEGRAPHY. 



section of tlie earth plates of the artificial cable, near the beginning, is attached, sepa- 
rately, through a comparatively low resistance, i8o ohms, to the earth. Another short 
section of earth plate is connected to earth through a resistance of about 1500 ohms; 
the remainder through a resistance of about 180 ohms, as indicated. 



BALANCING A CABLE DUPLEX. 

At one time the procuring of a "balance" on a long submarine duplex cable waft 
a matter requiring much skill, but of recent years the actual cable is so closely dupli- 
cated by the artificial cable that it has become a comparatively simple operation. 

In taking this balance the nature of the signal, if any, produced on the home re- 
''•order by depressing the home keys is an indication as to the location of that section 

FIG. 213. 



5ff^n/s 





B 



^m^^Y- AC 

iiJLjUUUUlEM 



^' 



ISO oJuns 




1500 ohms 



\180oJim6 



CABLE DUPLEX— MUIRHEAD ARTIFICL^L CABLE. 



of the artificial cable which is not in "balance " with the "real" cable. For instance, 
if a sharp, well-defined signal, is returned, it may be expected that the near end of the 
artificial cable requires adjustment. If the signals, on the depression of the home key, 
are faint, the lack of balance is further on in the box, etc. 

The balance is, of course, practically perfect when the home recorder is unaffected 
by the home keys. 

As a rule, after the cable has once been balanced any slight changes that may 
occur are easily compensated for by the small condenser c^ and the small coils in br. 
In practice, these latter adjustments are made about once in twenty-four hours, and it 
is not necessary to stop the transmission of telegrams to effect the necessary changes. 

In the case of the Commercial Cable Company's Atlantic cables, a change in the 
balance of the main artificial cable is only required about twice in the twelve months; 
namely, in March and October, and this only necessitates a slight alteration in the loca- 
tion of "ground " resistance in one of the boxes of the artificial cable, as at:r. Fig. 213. 

This change in the main balance, which occurs uniformly at the times stated, ie 
doubtless due to variations in the temperature of the ocean. 



BROWN AND ALLEN RELAY. 251 

The "static" or "inductive" cajjacity of an Atlantic cable is about one-third 
microfarad, per knot. Its resistance is about 3 ohms, per knot ; for ex impie, the total 
length of the Canso-Waterville Atlantic cable of the Commercial Cable Company is 
2345.72 knots; its resistance, 6,997 ohms, and static capacity, 876 microfarads. 

The speed of telegraphic signaling has been found to be inversely proportional 
to the product of the resistance of the conductor multiplied by its capacity. Hence, 
in its high resistance and capacity, a long submarine cable possesses elements conducive 
to slow signaling. The resistance of a wire conductor decreases inversely as the 
square of its diameter ; its capacity increases directly as the area of its surface. Hence, 
by increasing the diameter of the conductor, its resistance may be decreased in a 
greater ratio than its capacity is increased, consequently, by increasing the diameter 
of a conductor of given length, the product of capacity and resistance (or, as it is 
termed, kr) may be reduced, and in that way the rate of signaling may be increased, 
other things being equal. 

An example of this may be offered. 

Assuming a cable of a given length having a total resistance of 15 ohms and a 
capacity of i microfarad, and having a diameter of 90 mils. The product of resistance 
and capacity will be 15 X i = 15. Let the diameter of the conductor now be made 
100 mils. From the foregoing the resistance of the conductor will now bCjioo^ : 90^ 
: : 15 :x — 12.15 ohms, and the capacity will now be, 3.1416 X 90 : 3.1416 X 100 :: 
i: x; that is, 282.744 : 314.160 :: i : x ^^ 1. 11 microfarads, and the product of these 
will be 12.15 X i-ii — 1348, showing that, by the increase of diameter, the signal- 
ing has been increased in the ratio of 13.48 to 15. 



The Brown and Allen Relay. 

It has already been intimated that the time required to charge and discharge a 
long submarine cable to the extent necessary to operate oidinary Morse relays pre- 
cludes the use of such relays for practical purposes in submarine telegraphy. 

The result of charging, for instance, an Atlantic cable with the amount of current 
used on land lines, would be that the distant relay would simply remain closed, since 
the intervals during which the key would be open would not suffice to permit the cable 
to properly discharge. In other words a retarded current of ample strength to attract 
the armature would, while the key is momentarily open, continue to flow tlirough the 
distant Morse relay. There would be, however, a diminution in the strength of current 
in the cable during those intervals, but only of a slight character — not enough, as just 
intimated, to allow the armature to yield to its retractile spring. These variations 
will, however, be somewhat more pronounced when the " double current" method of 
signaling is used, that is, the method in which the current is reversed in direction 
by the opening and closing of the key, in the manner previously explained.* To avail 
of these slight changes of current strength, a very sensitive instrument, termed the 
"Brown and Allen" relay, has been devdsed, and has been successfully employed on 
submarine cables of about 600 knots in length, in connection with the double cur- 
rent method of siffnalinsj. 



See also Chap. XVII I, pages 2S7, 28S. 



282 



AMERICAN TELEGRAPHY. 



FIG. 214. 



This relay is shown iu Fig. 214. It consists of a coil of fine wire wound around 
a core of soft iron. The ends of the core extend beyond the coil and pass between 
the poles of two permanent magnets N, s; N, s. A current in the coil tends to make 
one of the ends of the core a north pole ; the other a south pole; consequently, the 
north end will be attracted to the south pole of its permanent magnet, while the 

other end of the core will be 
attracted to the north pole 
of its permanent magnet. 
The coil is rigidly attached 
to the core, but is insulated 
from it, in the usual man- 
ner; and the whole is sus- 
pended by a fine fibre, as indi' 
Gated. So far, the arrangement 
is virtually a form of polar- 
ized relay, delicately poised. 
There is, however, in addi- 
tion, an attachment to the 
instrument which imparts to 
it, sensitiveness; namely, a 
light metal pointer, termed a 
"jockey," pivoted at a,. 
somewhat in advance of the 
middle of the coil, and ex- 
tending beyond its ends. One 
of the ends of the "jockey" 
is placed between the ends 
of the stops s', s", one of 
which has a contact point and 
is part of a local circuit. 
The play of the pointer be- 
tween these stops is very lim- 
ited; about the one thousandth 
of an inch. A delicate 
spring, resting on the pivot 
of the jockey, and controlled 
by a small nut ;z, bears on 
THE BROWN AND ALLEN RELAY. thc polutcr just Sufficiently 

to insure contact for the local circuit and to cause the pointer to follow, when unre- 
stricted, the coil in its movements. But the pointer is not so rigidly attached to the 
coil as to check the motion of the latter when the jockey reaches its contact point or 
back stop. In other words, should the coil, for instance, be deflected to an angle of 
1° or more, the " jockey " will not follow it more than ywoo ^^ ^^ inch, and yet, 
on the slightest recoil, and subsequent slight advance, of the relay on its axis, the 
pointer will fall back and again advance wit]i it, etc. 




JACOBS DUPLEX. 



283 



The coil is held, normally, in a central point between the permanent magnets, 
by the springs p, p'. The presence of a current in the coil overcomes this balance, by 
magnetizing the core. The local connections of the pointer are so arranged that a 
current in tlie coil will press the jockey against its contact point, closing the local 
circuit. A very slight diminution of the current allows the pointer to fall away from 
the contact point. In practice, frequently, several makes and breaks are made in the 
local circuit without any perceptible motion of the relay. 

TJie relay virtually corresponds in its action to that of the mirror or recorder on 
longer submarine cables, the frictional connection of the jockey with the relay, per- 
mitting, as it were , a " shifting " zero ; the minute changes in the magnetic strength 
of the coil, due to the transmission of signals, while not sufficient to allow the relay 
to return to its normal zero between signals, being, yet, sufficient to actuate the point- 
er, and thus to operate the local sounder, at a fair rate of speed. 



The Jacobs Duplex, 



Submarine cables of moderate length, such as those referred to, on which the 
Brown and Allen relay may be used, are sometimes made up of two conductors. 

It is apparent that if two conductors of a cable of any considerable length were 



FIG. 215. 




C 




\^' 



JACOBS DUPLEX. 

operated separately, marked "inductive " effects from wire to wire might be expect- 
ed, especially in view of the sensitiveness of the receivhig instruments necessarily 
employed. To avoid these effects and yet retain the practical equivalent of two con- 
ductors, an arrangement known as the " Jacobs " duplex is used. 

The principle of this arrangement is shown in Fig. 215, and, for simplicity the 
ordinary Morse method of signaling is there assnmed, c, c are the two conductors of 
the cable, which are joined at x and x' . Between .r, x' and the ground e, e,' instru- 



i.e. of a given direction. 



284 



AMERICAN TELEGRAPHY. 



ments and battery are placed at each end of the cable, x and y, respectively. Bridge 
wires w^ w\ iu whicli are placed instruments and batteries connect the two conduc- 
tors at each end, as shown, forming a Wheatstone bridge arrangement, of which the 
resistances a b and a' b' are arms. 

From what has already been stated relative to duplex telegraphy, it will be evi- 
dent that, if the resistance of the conductors c c from x to^', and that of the arms a, a\ 
b, b', be equal, the opening and closing of the keys k, k' will produce no effect upon 
the instruments in the bridge wires, but will operate the relays k r'. Thus 



signals 



FIG. 215 a. 




toJWi 



may be sent from k to e' and k' to e, without affeuimg the relays r or r\ in the bridge 
wires. On the other hand, the effect of opening and closing the key k or k\ in 
the bridge wires, will be to operate the relays r or r\ practically as if they were in a 
metallic circuit disconnected from the bridge arms and earth, except, of course, that, 
by the division of the current (due to the bridge wire batteries) between the conduc- 
tors proper and the bridge arms, the current reaching the distant end of the cable is 
diminished somewhat; and this fact necessitates the placing of sufficient resistance 
in the bridge arms a b, a b' to avoid any tendency to short circuiting those batteries 
via the said arms. In the practice of this method condensers are sometimes placed 
in the bridge arms in place of, or in addition to the resistance coils a b. None of the 
current from the bridge wire batteries passes to earth via the relays p r' and, con- 
sequently, those relays are not affected by those batteries. It thus results that sig- 
nals may be sent from the instruments in the bridge wires which will not be notice- 
able on the instruments e, e' in the wires leading to earth, and, vice versa. 



JACOBS DUPLEX. 285 

As this arrangement provides the equivalent of a metallic circuit there will be 
no '* interference " from wire to wire during the transmission of signals from either 
end. It will be understood,, however^ that the same electrical action that would oc- 
cur on a simple metallic circuit in the transmission of signals, or that would occur on 
two wires connected at x, x\ without the bridge wire batteries, does not take place 
in this arrangement when both " sides" are in operation, but, instead, there takes 
place a practically similar action to that described in connection with the operation 
of the polar duplex system, in which the batteries at the opposite terminals, whether 
opposing or coinciding as to direction, equally co-operate to produce the desired sig- 
nals at the terminals by bringing about variations in the potentials which tend to 
that result. 

This " duplex" as arranged for practical working is outlined in Fig. 215^. 

A and B are the conductors of the cable, x, y are assumed to be the terminal 
stations, r, r' in the bridge wires and e, r in tiie "single " wire between x, x and 
the ground, are "mirror " galvanometers or "recorders." c, c' and c^c' are condensers, 
placed in the bridge arms, as shown. Those condensers are of practically equal ca- 
pacity. Small resistances a b, a' b' may be j^laced in the arms, k k' are the ordi- 
nary cable reversing keys. The 3-contact switches s, s, s', s', are used to change from 
"sending" to "rec^eiving," as may be desired. The switches s and s are set for 
receiving, s' and s' for sending. The middle contact on the switches is designed 
to allow the " charge " of the cable to escape to earth, or to equalize itself, before 
the recorder or mirror is placed in the circuit. 

If the cable is not too long, " Brown and Allen " relays may replace the mir- 
rors. 

It will be observed that this arrangement furnishes greater facilities than one 
wire duplexed, since two messages may be simultaneously sent from either end or 
one messaa^e from each end, at the same time. 



Automatic Transmission: — Two forms of automatic transmitters are in use in 
Submarine Telegraphy. One, the Wilmot transmitter, a modification of the AVheat- 
stone transmitter. The messages are prepared for transmission on a paper ribbon 
on which, for this purpose, three rows of holes are perforated. These upper and 
lower holes control the polarity of the current sent into the cable ; the middle row is 
employed as in the Wheatstone transmitter. The other transmitter is due to Cuttriss. 
This latter device is novel in that by an intermittent motion of the perforated ribbon 
it is practicable to vary the duration of current and earth contacts in any proportion, 
the one to the other. Another feature of this transmitter is that by means of a cam 
device the contacts are never opened while current is passing them. Hence sparking 
is avoided. 

The main advantages of automatic transmitters for this work are that a greater 
speed is attained, and also a more uniform signal is transmitted than is possible in 
manual transmission. Hence the operators are enabled to translate the received sig- 
nals with greater accuracy. 



2^S<^ 



AMERICAN TELEGRAPHY. 



BROWN S CABLE RELAY AND REPEATER. 

Many attempts have been made to devise a long submarine cable relay, but until 
recently without success. The difficulty has been to secure an instrument that 
would respond to the very miuute currents tliat reach the receiving end of such a 
cable, and especially one that would respond to the very slight variations of current 
that occur between the pulsations of similar polarity, as for instance in the letter 7^, 
at the ordinary rate of signaling on such cables. In the siphon recorders employed 
on long submarine cables friction is practically eliminated in the manner described, 
namely, by keeping the siphon in a state of vibration. The varying or wandering 
zero is not found to be a bar to easy reading of the ink record by expert operators. 
When the attempt is made, hoAvever, to utilize a relay operated by such currents to 
repeat the message on to another cable, it is necessary that the pointer or tongue of 
the relay come back to a fixed zero between signals. 

An ingenious cable relay due to Mr. S. Gr. Brown, described in the ''Journal 
of the Institution of Electrical Engineers," No. 157, 1902, has been found to meet 
these requirements. This relay is outlined in Fig. 286a. In this c' is the cable, c is 



FIG. 286a. 










BROWN S CABLE RELAY. 



the interposed condenser, R is the coil of the ordinary siphon recorder, F is a pivoted 
rod which is joined to the coil r by two silk or quartz fibers q q. A tongue t is carried 
by the arm f as shown. The tongue is a fine siphon glass tube, through which 
runs a phosphor-bronze wire, to the right end of which is soldered an iridium contact- 
point which normally rests lightly on the middle segment of a drum D. This mid- 
dle segment is insulated. Two other segments d d' of this drum are of metal, and 
are in metallic contact with the brushes 1) I)\ each of which is part of a local circuit 
containing dot-and-dash relays r r' and a battery B, one or the other circuit being 
completed when the contact point of t rests on either segment d d\ or both will be 
open when t is on the middle segment, inasmuch as t is also a part of the said cir- 
cuits. When the drum D is at rest the tongue remains on the middle segment 



BROWN'S CABLE RELAY AND REPEATER. 285^ 

regardless of whether signals may be arriving or not, the strength of the currents 
in the coil k not being sufficient to move the tongue against the friction of the point 
on the drum. But when tlie drum is rotated at the rate of about 150 revolutions 
per minute the friction is apparently eliminated and the pointer responds to each 
impulse of the coil. The condensers s s, of two microfarads each, which shunt 
the contact-point of t, are found to be of much utility in impro) ing the contact, 
especially when the surface of the drum is very smooth, the reason for Avhich result 
is not known. 

This, however, does not get rid of the variable zero of the coil, which would ren- 
der the operation of the relay of no utility, as the pointer would not get back to the 
insulated section between signals. To overcome this defect Mr. Brown has designed 
a "local correction," which, briefly, consists of setting up currents through an extra 
winding in the coil, not shown, of such character and strength that as the cable 
current dies out the local current increases at the same rate. This is brought about 
by means of the current from a local battery and the relays r r', which is sent 
through a circuit, including the extra coil, "having considerable retardation, and 
made up of a condenser placed between two high resistances, condenser and resist- 
ances being made capable of minute adjustment. ... L is a large inductive 
shunt of 30 ohms resistance joined across the terminals of n." This device suffices 
for comparatively short cables, but, as the inventor notes, on longer cables at high 
speed many of the originating impulses are obliterated from the received signals 
whenever successive impulses of the same polarity occur. There is no difficulty 
on the part of the operator in translating the characters on the tape, since h.3 reads 
them by the space they occupy on one side or other of the zero line. When, however, 
it is desired to repeat from one cable to another it may be essential to reproduce the 
missing beats or " ripples.'"' To this end Mr. Brown employs an interpolating device, 
" whose action resembles that of the automatic transmitter at the originating station, 
with this difference, that the movements of its transmitting levers, instead of being 
governed by the perforations in tape, are governed by the motions of the relay 
tongue." This interpolator consists of two rota ting-cam arrangements, operated by 
suitable mechanism, which, under the control of the relay tongue, open a local dot- 
and-dash circuit as many times as there may be characters, dots, and dashes in a letter. 
So that, for example, "if, Avhen the letter h is received, the tongue of the drum relay 
remains in contact with the dot side throughout the four beats of the letter, simply 
producing a long contact on the dot relay, this long signal is split up by the dot 
cam of the interpolator and transmitted as four dots." In a similar way a long con- 
tact on the dash relay, representing, say, the letter 0, would be split into three dashes 
by the dash-cam of the interpolator. The speed of the interpolator mechanism 
must be synchronous with that of the transmitter. 

This relay is now in operation on several long cables. 



236 



AMERICAN TELEGRAPHY. 



UNDER WATER TELEGRAPHY. 

A number of experiments, more or less successful, have been made relative to the 
transmission of telegraphic signals, electrically, across water, without the aid of wires. 
One method for this pur^iose is to place in the water, at some distance apart, the 
terminals of a conductor connected with a battery and transmitting apparatus, on 
one side of a river or harbor; while on the other side of the river the terminals of a 
wire, connected up with receiving apparatus, are similarly placed in the water. VVhen 
the distance across is not too great the signals transmitted may be received. Hither- 
to no very practical use has been made of the results thus obtainable. 

The device illusti-ated in Fig. 216 is intended as a mechanical means of commun- 
ication between vessels at sea, during fogs, but, so far as known to the present writer, 
it has not passed the experimental stage. 

The manner of its operation will be apparent. A bell, B, is lowered into the 
sea, by means of a rope and pulley, into a position where it may be struck by the 
hammer h, which is movable from shipboard. The receiver is along, bent, trumpet- 
shaped tube T, which is lowered into the water from another vessel. Both vessels 
are assumed to be provided with receiving and transmitting apparatus, which 
may be placed at the bow or stern, as desired- 

FIG. 316. 




The sounds produced by the strokes of the hammer upon the bell are propagated 
by the water to the mouth of the tube and thence to the ear of a listener at the "re- 
ceiving " ship. 

Experiments have shown that signals can be transmitted in this way to a dis- 
tance of about half a mile, but at a distance of 2200 yards the sound is not percep- 
tible. 



CHAPTER XVIII. 



AUTOMATIC TELEGRAPHY. 



THE WHEATSTONE AU"TOMATIC SYSTEM. ANDERSON CHEMICAL AUTOMATIC SYSTEM — ■- 

FAC-SIMILE TELEGRAPHY. 

Rapid automatic telegeaphy. — The term Automatic Telegraphy, aj^plied to 
the transmission and reception of telegrams, ?tc., is hardly sufficient to include 
definitely, i,he different practical systems of automatic telegraphy. 

For instance, a system may be partly manual and partly automatic, as in the 
case of the Morse system when a recording register is used as receiver; or in that of 
the Phelps '' motor " printing telegraph system, in which the manually transmitted 
messages are received in Roman letters on a paper strip. Nor does the term dis- 
tinguish between those automatic systems in which the messages are recorded in ink, 
and those in which the signals are recorded by electro-chemical action. Elsewhere 
herein the term, " ink recording " automatic telegraphy, is applied to systems in 
which the signals are received by ink recorders, and the term, '• chemical " automatic 
telegraphy, to systems in which electro-chemical decompositions produce the records 
of signals. 

As, however, there are instances of both of these systems, in the operation of 
which the rate of triusmission is comparatively slow, namely 30 to 60 words, per 
minute, the writer has chosen the term, " rapid " automatic telegraphy, to distin- 
guish the systems by which the signals are transmitted at a rate of speed ranging 
from, say, 300 to 2000 words, per minute, from those by which the signals are trans- 
mitted at the first mentioned rate of speed. 

In the transmission and reception of Morse or other code signals, rapid chemical 
automatic telegraph systems usually employ at the sending end, in a manner to be de- 
scribed, specially prepared, perforated paper^and contact pens^ and, at the receiving 
end, chemically prepared paper, upon which the electrical pulsations corresponding 
to the signals transmitted are caused to record such signals, by decomposing the chem- 
ical solution in whi(;h the receiving paper liad previously been immersed. Rapid ink 
recording automatic systems usually employ somewhat similar devices at the trans- 
mitting end, but, at the receiving end, an ink recorder or " register " is employed to 
record the signals. 

In telegraphy, the term, "single current," is applied to systems in which currents 
of one direction only are employed; for example, the ordinary Morse system. The 
term, " double current," is applied to systems in which the direction of the current is 

287 



288 AMERICAN TELGRAPHY. 

reversed at each opening and closing of the key, or pole-changer, as, for instance* 
in the ])olar duplex system. 

Owing to the higher rate of transmission of electrical pulsations that can be 
attained over a telegraph circuit by means of the double current method of signaling, 
that method is almost invariably used, both in chemical and ink recording automatic 
systems; as, for example, in the case of the Wheatstone automatic duplex system, 
to be described presently, in which the transmitter acts as a double current " sender," 
or pole-changer. 

At a high rate of speed of transmission, even o;i wires of only moderately high elec- 
tro-static capacity, the signals tend to run together, causing prolongations of the char- 
acters and, in some cases, a continuous dash, on the paper tape. These prolongations 
are technically termed "tailings." This result is due to a cause similar to that de- 
scribed in connection with the attempt to operate the ordinary Morse apparatus on 
long submarine cables, namely, that the wire has not time, between signals, to clear 
itself of the previous charge before a succeeding charge again " fills " the line. This 
tailing effect, obviously, depends largely on the length of the circuit and upon its 
electro-static capacity. 

When a charge of one polarity is followed by a current of opposite polarity on 
the wire, as in the double current method, the effect is to neutralize the previous 
charge, thus cutting short the tailings; and it is this which conduces to the higher 
speed of transmission by the double current method in rapid automatic telegraphy. 
It may be mentioned, however, that the same result, as regards tailings, will, of course, 
follow, even when the double current method is employed, when the rate of trans- 
mission exceeds the maximum carrying capacity of the wire or the instruments. 

The manner of preparing messages for transmission by rapid automatic trans- 
mitters, has generally been to punch holes in a paper tape, either in a single row, 
when the single current method is to be employed, or in two rows, when the double 
current method is to be utilized. In some cases the messages have been prepared for 
transmission by the deposition of an insulating, quick- drying paint, or paste, upon a 
cylinder, in the shape of the Morse characters. 

As a rule the perforations have been made hitherto by the depression of a "punch " 
which, at each depression, perforates the part of a letter. For instance, one depression 
of the instrument punches the symbol for a dot, the next depression that for a dash; 
this requiring as many depressions to compose a letter as there are characters in the 
letter. In other instances, punching apparatus has been devised by means of which 
all of the characters composing any given letter have been perforated at one de- 
pression of a key. Where the single current method is employed, and wlien but 
one row of perforations is required, the preparation of the paper has been accomplish- 
ed with comparatively little difficulty, as, in that case, it is only essential that long 
and short holes, corresponding to dots and dashes, be perforated in a straight line. 
But, when the double current method is utilized, the machinery required to punch 
the required number of characters at one stroke in two rows is of a somewhat more 
complicated nature and, consequently, more liable to get out of order. For this 
reason, perhaps, the single character punching apparatus has been adhered to in the 



AUTOMATIC TELEGRAPHY. 28^ 

most successful of the double current automatic systems, for instance, as in the Wheat 
gtone automatic system. ^ 

In preparing messages for transmission by the " insulated " cylinder plan referreci 
to, the paint is deposited on a revolving, and laterally moving, metallic cylinder, by 
means of a flexible spout in communication with a suitable reservoir containing the in- 
sukiting 23aint ; the spout being attached to the armature of a sounder, or relay, in a 
circuit controlled by a Morse key. In effect the operation of the punched paper and 
the " painted " cylinder is the same, unless when, as in the Wheatstone automatic 
system, the perforated paper is used to control the operation of the transmitter. 

When the perforated paper is used to transmit directly, the electrical pulsations, 
it is caused to glide over a metallic cylinder, or wheel, which forms part of the line 
circuit. Above the paper, and resting on it, ape placed one or two metallic brushes, 
or contact pens, according as it is the single or double current method that is em- 
ployed. These pens also form a part of the line circuit. As the paper passes over 
the cylinder the pens fall through the holes in the paper and complete the circuit. 
In the double current method one pen may be connected with one pole of the batv 
tery; the other pen with an opposite pole, so that the opposite poles are placed tc? 
tile line as the respective pens make contact with the cylinder. Analogously, in the 
case of the "painted" cylinder, a contact pen is caused to rest upon the cylinder, and 
as the latter revolves and moves laterally, the circuit is opened and closed according 
as the pen passes over insulated or non-insulated parts of the cylinder. 

Systems which employ contact pens in the manner just stated may be termed 
''direct contact '' transmitting systems, in contradistinction to those in which the 
prepared paper is caused to control the operation of the transmitting instruments, of 
which latter the Wheatstone automatic system is also an example. 



CHEMICAL AUTOMATIC TELEGRAPH SYSTEMS. 

At one time, both in Europe and in the United States, rapid chemical automatic 
systems were extensively employed in commercial telegraphy, but to-day it is ques- 
tionable whether one such system is in practical operation. In many instances, it is 
true, electro-chemical methods of recording signals are now employed in police, 
fire alarm and similar telegraph systems, in this country. 

In Europe, for various reasons, chemical automatic telegraphy has been practi- 
cally superseded by ink recording systems, and, in this country, mainly by the ordinary 
Morse manual system. 

Until w^ithin a few years chemical automatic telegraphy was the only method 
of rapid telegraphing attempted in this country, but, at present, as elsewhere re- 
marked, the Wheatstone automatic system, with its ink recording apparatus, is now 
being operated quite largely. 

The receiving apparatus of those chemical automatic systems in which the Morse 
code characters are recorded, so far as the actual recording of the signals is 
concerned, is practically the same in all cases. It is outlined in Fig. 217. A cylin- 
der, or wheel d, with a flat periphery, composed of some metal not decomposable by 



290 



AMERICAN TELEGRAPHY. 



the chemicals used, forms part of the circuit. Metal pens, or styles p, form another 
part of the circuit. Between the cylinder and the pen, or pens, the chemically pre- 
pared paper p', still damp from immersion in a chemical solution, passes. 

The principle involved in the operation of chemical telegraphy is that of the de- 
composition of the electrolyte through which the current is caused to pass. The liquid 
chosen as the electrolyte must be one readily decomposable by the current. In other 
words, one in which the component parts are held together in a, chemically considered, 
somewhat unstable manner. At the same time the combination must be one which 
will not, in its normal condition, attack the parts of the apparatus with which it may 



FIG. 217. 



^(ytJl^^' 




CHEMICAL AUTOMATIC RECEIVER. 



come in contact, that is, the j^en or cylinder of the receiving apparatus. But, at the 
same time also, the combination, or mixture, as in part the chemical solution sometimes is, 
must contain elements, or sub-combinations, which will either, when freed by tlie cur- 
rent, produce a mark on the paper or else combine with the metal of the receiving pen 
to produce such a mark during the progress of the current through the paper. For 
example, if the paper be saturated with a solution of potassic iodide dissolved in water, 
the action of the current will separate the iodine from the potassium, when the for- 
mer will appear on the paper as a brown line. 

Again, it is known that one of the most characteristic properties of iodine is the 
production of a clear blue color when combined with common starch. The iodine 
for this purpose must be free, or uncombined. If then the solution, or mixture, em- 
ployed, be one containing potassic iodide, and starch dissolved in water, the action of 



AUTOMATIC TELEGRAPHY. 29I 

the current will set free, as before, the iodine, which, combining with the elements of 
the starcii, will produce a blue mark on the paper. 

The latter solution is, in practice, usually prepared in the following proportions: 
I part potassic iodide; 20 parts starch paste; 40 parts water. The stain produced by 
this solution, however, while very readily produced, that is, with a minimum of cur- 
rent, is very transient, fading almost as soon as exposed to the air. When this solu- 
tion is used a platinum pen is employed to conduct the current to the paper. 

Another solution from which the current sets free an acid that attacks the iron or 
steel pen, thereby forming a combination which appears as a blue-black mark on the 
paper, is composed as follows : 5 parts prussiate of potash ; 150 parts ammonio ni- 
trate ; I o parts water. 

The essentials of a solution for the sensitive paper used in chemical telegraphy 
are that it shall be easily decomposed; produce a permanent record; be retentive or ac- 
cumulative of moisture, and a fair electrical conductor. 

In the case of the last mixture given the object in using the prussiate of potash is 
to supply the acid radical cyanogen, which attacks the iron pen, forming 
" Prussian " blue, permanent marks, on the paper. That in using the ammonic nitrate 
is to maintain the paper in a moist condition, which it does by absorbing moisture 
from tlie air, the ammonic nitrate being a deliquescent salt, that is, one which is ac- 
cumulative of moisture. The conductivity of the solution is sometimes increased by 
adding to it dilute sulphuric acid, not of sufficient strength to attack the metal 
pen. The marking always occurs at the positive contact point. 

Measurements of the resistance of the moistened chemical paper, between the pen 
and the periphery of the cylinder, have shown it to be between 250 and 300 ohms. 

Andeeson Chemical Automatic System. 

So far as is known to the writer there is but one chemical automatic system now 
extant in this country, designed for the rapid transmission of telegrams, on wliich 
work of any kind, practical or experimental, is being done; namely that of the Ma- 
chine Telegraph Company. The objects striven for by the inventor of this system, 
Mr. Frank Anderson, are maximum rapidity consistent with accuracy of transmission 
and simplicity of the apparatus. The Anderson system belongs to that class of auto- 
matic systems in which Morse characters are transmitted by means of perforations in 
a strip of paper and in which the characters are recorded either by ink recorders or by 
electro-chemical decompositions on chemically prepared paper; it is, however, best 
known as a chemical system. 

In Fig. 218 the connections of the Anderson system are shown, theoretically. 
B is a main battery at a transmitting station x. t is a metal cylinder rotated by 
suitable apparatus, s is a contact pen or brush, p is a perforated paper tape passin^r 
between the cylinder and brush. At the receiving station y, t' is a metal cvlinder 
also rotated by suitable mechanism, p' is a chemically prepared paper tape which passes 
between the cylinder and pen s'. c is a condenser and R is a rheostat "shuutino-'' 
the condenser. 

The transmitting strip is prepared by punching large and small holes in one row, 
as seen in Fig. 218. 



2Q2 



AMERICAN TELEGRAPHY. 



Since but one row of holes is used in the perforated paper it will be evident that 
some means must be provided for obtaining the equivalent of the * double " current 
metliod of transmission previously referred to, otherwise a very high rate of speed 
could not be expected. This equivalent is furnished by the condenser c, at the dis- 
tant station which, on discharging, gives out a current in the opposite direction to thai 
of its charging current; the result of which is to cut off the "tailings. " 

Tiie operation of the condenser in this system is based on the well-known fact 
that this instrument receives a '' charge" when its poles, or terminals, are at differ- 
ent electrical potentials, and is immediately discharged when the charging battery , 
or electromotive force is removed and the condenser terminals are connected together, 

FIG 2l8. 

^ LIt\,c. 





ANDERSON CHEMICAL AUTOMATIC SY3TEM. 



or placed to earth ; the current of discharge being in the opposite direction to that of 
the current of charge. 

It will be seen. Fig. 218, that the pen s, paper p and cylinder t, at the transmit- 
ting station, form a circuit around the battery. This circuit is, however, only com- 
plete when the pen drops through one of the holes in the paper; the effect of which is 
to short-circuit the battery b and, consequently, to suddenly drop the potential on 
the line wire at x. Normally, therefore, as when the pen is resting on the paper, the 
full battery is to the line. At such times the condenser c at y is charged with a cer- 
tain polarity, the amount of charge measurably depending on the resistance r. At 
the moment when the transmitting brush falls into a hole in the paper and the po- 
tential on the line is dropped practically to zero, the condenser, c, at once parts witli 
its charge, producing a current in a reverse direction to that of the charging current, 
thus interrupting the flow of marking current through the paper. The resistance of r 
is regulated so that the current from tlie condenser shall be sufficient to secure well 
defined and sharp marks on the paper; otherwise, in some cases, the marks would be 
imperfect, showing that the discharge current from the condenser was too strong. 



AUTOMATIC TELEGRAPHY. 293 

Hence, by this means, there is obtained the equivalent of a double current at the 
transmitting end, with the advantage of a prompter action in the matter of the ap- 
plication of the reversed current, to diminisli the tailings, by having the generator 
of the " double current " at tie receiving end ; an additional advantage consisting in 
the fact that the amount of charge and discharge may be readily adjusted at the 
receiving end Avithout reference to the transmitting battery, excepting,of course, that the 
latter must have sufficient electromotive force to provide a working margin at the re- 
ceiving end. 

Ill the Anderson arrangement in the act of short-cirCuiting battery b, a direct path 
to earth via x is provided for the " static " discharge of the line, leaving a minimum 
to be neutralized by the condenser at y. In other chemical systems where a con- 
denser has been used as at y, but in which the direct earth at the transmitting station 
has not been employed, it was frequently found that the condenser, not having suffi- 
cient opportunity to discharge between impulses, would become charged or, so to 
«peak, *' clogged, " and would remain virtually inoperative after a few impulses. 

Ordinarily, in chemical automatic systems of this class the battery has been 
placed to tht line when the contact pen touched the cylinder, in the same way 
that the current passes to the line when the key is closed in the Morse system. 

It has been shown that, in the Anderson system, the signals are transmitted by 
an o^)i)Osite method, namely, that when the transmitter is in contact v/ith the cyl- 
inder the battery current does not pass to the line. If, therefore, the holes in the 
paper were made in lengths to correspond to dots and dashes, signals would be re- 
ceived, as it were, on the "back" stroke. Hence it is clear that a special method of 
preparing the holes in the paper must be availed of. This method consists in so 
perforating the paper strip that the uncut paper between the holes represents the 
dots and dashes of the alphabet. Consequently, as, in the Anderson system, it is 
only when the transmitting contact pen is passing over the uncut parts of the paper that 
the charges pass to the line, the result is that " straight" dots and dashes are recorded. 

A specimen of the punched paper strip used in this system is shown in Fig. 219. 

In the figure, characters in dots and dashes are placed under the holes. The 
large holes produce the space between letters. Two large holes cutting into each 
other produce the space between words. The blank spaces on the paper between the 
holes produce dots or dashes, according to their respective lengths. 

FIG. 219. 
a b c d e f g li i ] 



The holes represent letters of the alphabet from a to k. Spaced letters are not used 
W this alphabet. iSuch letters are assigned special characters. Tl us : 

Cj' O K — Y Z 



294 



AMERICAN TELEGRAPHY, 



Fig. 220. 



In experiments over actual circuits of about 2,500 ohms resistance and 1,000 miles 
in length, signals have been transmitted clearly by this system at a uniform rate of 
600 words,per minute^ during all kinds of weather and without any change in the ad- 
justment of the apparatus. The electromotive force used was 250 volts. The con- 
denser at the receiving end had a capacity of 4 microfarads and was shunted with 

iO;,ooo ohms resistance. On a 
circuit 360 miles in length 
and having about 700 ohms 
resistance, 3,000 words, per 
minute, have been transmitted 
and clearly reproduced at the 
receiving end. In regular 
practice such ^ high rate of 
speed would hardly ever be 
necessary; probably 1,500 
words, per minute, would 
suffice. 

In the act of transmitting 
messages at high rates of 
speed, say, 2,000 words, per 
minute, the paper at both 
ends is shot over the respec- 
tive cylinders at the rate of 
about 400 feet per minute. 

It is very plain that at 
such a rate it is quite im- 
possible for the attendant at 
the receiving station to follow 
intelligently the signals as 
they arrive and are record 
ed on the paper; everything 
appearing as a straight line 
or as a blank. 

In regular practice this inability to follow up the received signals has frequently 
been a source of much vexatious delay owing to the fact that any confusion of sig- 
nals due to the occurrence of momentary interruptions of the circuit has gone un- 
noticed until the dispatches reached the hands of the transcribing clerk. This has often 
necessitated the repetition of many messages in order that corrections might be made. 
To avoid this defect of 4-apid automatic telegraphy in the Anderson system, a 
low resistance telephoi^ is placed in the circuit. The effect of the rapid transmission 
of the signals is to cause a distinct hum in the telephone which is clearly heard, 
but upon the occurrence of wire trouble the instrument gives out a broken sound 
which serves as an instant warning to the attendant, who at once stops the instru- 
ment and takes any action necessary. The transmitting end may be similarly equip- 




ANDERSON PAGE AND LINE CHEMICAL RECORDER. 



ANDERSON CHEMICAL AUTOMATIC TELEGRAPH. ^95 

ped and thus the safeguards against errors are doubled. This device is peculiar to 
the Anderson system. 

Another device which is useful in aiding the prompt detection of wire trouble 
consists of an arrangement whereby the signals are received on sheets of paper in- 
stead of on the ordinary paper tape. On the sheet, or page, the attendant can see at 
a glance, almost as soon as the signals are received, Avhether they are being recorded 
properly or otherwise. 

The manner in which this result is effected in the Anderson system is shown in 
Fig. 2 20. The paper p, inj^age width, is shown passing over a long cylinder d, which 
is part of the line circuit w. The paper is chemically prepared in the usual way. 
Below the cylinder is a wheel b, having a metal periphery. This periphery is divid- 
ed into 6 segToients ^ b etc., as seen. The segments are insulated from each other. 
On this periphery rests a split contact pen, or spring, s, to which is attached another 
portion of the main line circuit. One of the tines of the pen is put slightly in ad- 
vance of the other. Six metal pointers, x^ project, at equal distances apart, from the 
periphery of the wheel, one from each segment of the periphery. On the end of each 
of these pointers a small metal pen, or needle, is placed, one of which is shown rest- 
ing obliquely against the paper p. 

As the wheel b is insulated from the cylinder D,it is obvious that the line circuit 
is completed through the periphery of wheel b, the pointer x and the paper p, to the 
cylinder. 

The wheel b and cylinder D are caused to revolve by any suitable means. The 
pointers are so arranged that as one is about to move off the paper p the next one 
moves on it, but before one pointer moves off entirely the contact spring s will have 
moved off that pointer's segment, thus cutting the right hand pointer out of circuit. 
Similarly the current will not have passed through the left hand jiointer until the 
contact spring has reached that pointer's segment. 

At the same time, the paper, in process of winding, is passing the cylinder. The 
result is that the left hand ends of the lines of characters are slightly lower than the 
right hand ends, but the distance between each line is the same. 

As it is essential that the contact spring s should not actually leave one segment 
imtil it has made contact with the next one, the spring contact is split in the manner 
stated and shown. In consequence of this there will be at the end of each line, on the 
page 23aper, a duplicate of the signals at the beginning of the next lower line. In order 
to avoid confusion from this cause two additional contact springs m, m', are caused to 
touch the paper on the cylinder, as shown. These form part of a local circuit l, in 
in which is included a local battery lb. The result is that two continuous vertical 
lines are electrolytically produced on each side of the paper. As the space between 
the points of the two contact springs m m' bears a fixed relation to the curves of the 
successive segments, all of the record to the right and left of the vertical lines is in 
duplicate. In reading the record the operator has simply to read all of the record to 
the left of the right hand line, ignoring all to the right of that vertical line, or all 
to the right of the left hand line, ignoring all to the left of that line. 

The chemical solution for the recording paper used in the Anderson cliemical 
automatic system consists of \\ ounces red prussiate of potash ; \\ pouiuls nitrate of 



296 



AMERICAN TELEGRAPHY. 



ammonia and i j^ound of muriate of ammonia, all dissolved in a gallon of 23ure rain 
or distilled water. 

According to Mr. D. H. Craig, to obtain the best results, paper intended for per- 
forating in automatic telegraphy, should be made from pure white cotton and linev 
rags, without the use of chlorine, or, if that is used, it should be washed in good 
water until every vestige of the chlorine has been expelled. Such paper does not 
dull the puncheS; or cutters, of the perforator when they are properly constructed. 

The pen used in the Anderson chemical automatic system is of very hue piano 
steel Avire. The pen is so adjusted that it can be conveniently lengthened or shortened, 
even while recording at the highest speed. 

The current, in its passage through the paper, decomposes the chemicals of the 
mixture, setting free an acid which attacks the steel wire, leaving, as a result of the 
action, permanent clear, blue-black dots and dashes on the paper. If a copper wire 
were used red dots and dashes would result. The wearing of the steel pen, thus 
occasioned, is provided for in the adjustment just referred to. Pure, soft iron wire is 
more sensitive than steel for this purpose but it has been found less reliable in practice. 



THE WHEATSTONE AUTOMATIC TELEGRAPH SYSTEM. 

Of the rapid, ink-recording, automatic systems of telegraphy, the Wheatstone is 
to-day, the best known. It has for many years been extensively used in Great Britain 
Pj(j^ 221 ^^^^ ^^^^ ^^^^ been employed on a number of circuits 

in this country for several years. 

The apparatus of the Wheatstone automatic 
system consists of a perforating machine, by means 
of which messages are prepared for transmission; 
a transmitter, which utilizes the perforated paper to 
transmit messages thus prepared, and a receiver 
which, being actuated by electrical pulsations set up 
by the transmitter, records them in ink, on stiff paper 
tape, as dots and dashes. 



THE PEEFORATOR. 

The perforator is shown, as a whole, in Fig. 
221. It consists essentially of a set of five metal 
tubes, or j^unches, each moving within a close 
fitting case, or guide, and which are capable of being 
pressed outwardly beyond the cases, by suitable 
mechanism. These punches, and the apparatus for 
operating them, are contained within the box b. 
their outside ends, have keen edges, and the paper 




J 2 5 

THE PERFORATOR, TOP VIEW. 



The hollow punches, at 

to be perforated is caused to pass, as seen in Fig. 221, close to the edges. 

The inner ends of the punches are adjacent to three rods or levers, which connect 
with three keys or discs, i, 2 and 3, Fig. 221, which latter are j^laced in a positioii 



WHEATSTONE AUTOMATIC TELEGRAPHY. 



297 



convenient for tlie operator. These keys are depressed by the punching operator who 
uses a rubber tipped mallet in each hand for the purpose. When a key is depressed 
certain of the cylinders are pushed outward through the paper strip. The keys 1,2 
and 3 are marked dof, space and dash^ respectively. When the dot key is depressed 
three vertical punches marked i, 2 and 3, in Fig. 222, are pushed outwards, and three 

vertical holes (o) are perforated. When the dash key is depressed four punches 



marked i, 2, 4 and 5, are operated, and four holes 



fo 1 



are punched. When the space 



key is depressed, but one punch, marked 2, is operated, and but one hole ( o ) is punched. 
A small star- wheel, the edge of which is seen as a short dash to the left of punch 

2, in Fig. 222, is so placed before the punches that the same action which pushes 

them out, also operates mechanism 
^^^' ^^^* which causes that wheel to re- 

volve, and as its teeth fit into the 
central, or space holes, justperfora 
ted, the paper is carried forward 
by that wheel with a regular mo- 
tion. By depressing these keys 
according to the requirements of 
the Morse alphabet, a message, re - 
presented on the strip of paper 
by vertical and diagonal circular 
perforations, is 




00 O GOO 00 O O 00 O 000 

GGOGOOOOOOOOOOOOOGOOOOOOOO 

O O OOOG 00 O 000 O OOG 



A 



B 



C 



^HE PERFORATER- 



D 

-SIDE VIEW, 



£; 



prepared for 
t r a n s mission 
by the Wheat- 
stone transmit- 
ter. When in 
perfect order? 
A portion of 



or gauge, the perforator punches 120 space, or center, holes, to the foot, 
perforated paper is shown below the box in Fig. 222. 

As the work of depressing the disc of the puncher is somewhat arduous, a pneu- 
matic arrangement is sometimes employed. 

In this arrangement the operator simply depresses a disc with his finger, which 
action opens a valve connected with an air tube, when a piston driven by the air pres- 
sure actuates the punches. 

THE TRANSMITTER. 

The actual transmitting parts of this instrument are outlined in Fig. 223. The 
rods, cranks, levers, etc., shown, are supported on the side of a box conttdning clock- 
work and gearing for driving the transmitter machiner5\ In the figure R is a ''rock- 
ing beam " carried by a shaft which enters the box through the frame. The shaft is 
given a rotary motion by suitable machinery within the box. l' and l are vertical 
rods, which, at their lower ends, are attached to the crank levers A a'. The crank 
levers are provided with horizontal connecting rods h, ii', the right hand ends of 
which pass through holes in the arms, or projections M m' from the disc i\ n 11, are 



298 



AMERICAN TELEGRAPHY. 



furnished with collets, or shoulders c, c', which, in certain positions, engage with the 
arms m m' and push the disc d back and forth. By means of adjusting screws f, f' 
the vertical rod l' is set to the left of l, a distance equal to the space between two 
consecutive horizontal holes in the perfprated paper. The rods are, normally, held 
towards these set screws by light springs k, k.' The springs s s give the vertical 
rods L l' a constant upward tendency, but their upward motion is checked by the 
pins p p' on the rocking beam r. For example, when the right hand end of the 
beam is making its upward motion the rod l follows the pin p upwardly. At the 
the same time the rod h, by its collet, pushes over the arm m of disc, d, as shown. 
Also, at the same time, the pin p' on r depresses the rod l' and this action withdraws 
the collet of connecting rod h', and thus permits the rod h to act freely on the disc 




^|.|.|.j.|.|.p, 
5 



WHEATSTONE TRANSMITTER THEORY. 



D by its arm m'. This disc is formed of two metal segments which are separated 
from each other by an insulating material. One of the segments is connected to the 
line, the other to the ground. A metal contact pin, i, 2, juts from each segment. 
Two crank levers cl, cl', connected with the battery b, are held against one or other 
of these pins by the springs shown. The movement of the disc d to the right or 
left is checked by limiting pins 1 1'. 

The disc d is virtually a pole-changer and these rods and levers simply replace 
the fingers of the operator in causing it to reverse the poles of the battery. In the- 
position of the disc D, in Fig. 223, a negative pole of the battery is placed to tho 
line. The j)erf orated paper is shown by the line above the vertical rods l l,' and it is 
supposed that the rod l has passed through one of the perforations in the j^aper. 
Assuming that there is another hole in the paper immediately opposite that one througk 
which L has just passed, then, when the next movement of the beam R permits the 
vertical rodL' to rise, it will, owing to its position to the left of l, as well as to the 
movement of the paper, to the left, pass through that hole, as shown in Fig. 224. By 
the downtv^ard motion of the right end of e the Rod l has been depressed. Conse- 



WHEATSTONE AUTOMATIC SYSTEM. 299 

quently, the collet c on h has been withdrawn, giving the collet c' on rod h' free 
scope to act upon arm m of disc b ; thus placing the rod cl' in contact with the 
right hand pin 2, on disc d, and the rod cl in contact with the left hand pin i, 
thereby reversing the polarity of battery b; for it will now be found that the positive 
pole of battery b is to the line. (Fig. 224.) 

J, in Figs. 223, 224, is a small wheel, termed a "jockey roller," held above 
the arm m, of disc d. It is held in position by a flat spring. Its fmiction is to assist 
in pushing over the disc d, when it passes the center, to either side, and it also insures 
a steady contact of the rods cl, cl', with the pins on the disc. 

The machinery within the transmitter box which actuates the beam R, also 
causes the star-wheel w to revolve, and its teeth, fitting into the central holes in the 
perforated paper urge it to the left a certain and regular distance at every up and 
down motion of the beam. As the central holes in the paper are perforated by the 
punching machine with precise uniformity as regards the position of the outside 
rows of holes in the paper, this stated motion of the pap'er insures that, whenever 
there is a lateral, or outside, perforation, it will always be in a position directly 
over one or other of the vertical rods l l' when they approach their maximum upward 
motion. 

The bent levers cl' and cl were formerly provided with a small set screw opposite 
the disc d to keep the contact points apart at the moment of reversal of the disc and 
thus prevent short-circuiting of the battery. The set screw was insulated from the 
lower lever. This device has been dispensed with in the instruments of recent manu- 
facture. 

In Morse telegraphy the dots and dashes are distinguished from each other by a 
short or long duration of the signal. In the Wheatstone automatic system, if a 
series of vertical holes such as these o {see .r, Fig. 223) were prepared on the paper 

tape and passed through the transmittei-^ the rods l, l' would make a full phase at 
every motion of the beam, and, inasmuch as this would cause regular reversals of the 
battery, a succession of dots would be recorded by the distant receiving instrument* 

When, however, a set of holes, such as these, So {see y^ Fig, 223,) is passed through 

the transmitter, the result is different. Namely: at its first upward motion the rod 
L will pass through the upper, or further, hole as in Fig. 223, (that is the hole nearest 
the frame of the transmitter) pushing the disc d to the right. At the next motion of 
the rocking beam the rod l' meets the paper at a point opposite the hole through 
which L had just previously passed, and its further ujjward motion is obstructed ; 
consequently, crank lever a does not follow pin p' the entire distance. The result is 
that the disc d is not pushed over and the battery is not reversed. In the next up- 
ward motion of l its phase is also checked by the paper, and the polarity of the 
battery, consequently, is still unchanged, until, at the n ext upward motion of l', the 
latter comes opposite and passes through the hole b (_>', Fig. 223,) and thus causes tlu 
arm m to push back the disc d, thereby reversing the poles of the battery. This de- 
lay in the reversal of the battery is sufiicient to make quite an appreciable distinction 
in the length of the signal recorded and, in fact, constitutes a dash. 

The effect of all this is that, depending upon the position of the perforations in 



300 



AMERICAN TELEGRAPHY. 



the paper, which have ah-eady been prepared for the purpose, dots and dashes are 
transmitted by the pole-changing disc d, in practically the same manner as the Morse 
operator would transmit them by an ordinary manual pole-changer, although, of 
courge, at a greater speed. 

A MODIFIED FOEM OF TEANSMiTTEK. — ^A ucw form of transmitter now much 

FIG. 224. 




WHEATSTONE TRANSMITTER THEORY. 

used in the British postal service, by which the speed of transmission is said to be in- 
creased very materially, is shown in Fig. 225. The change is chiefly in the arrange- 
ment of the battery reversing connections. The bent levers cl, cl', Figs. 223, 224, 

are dispensed with and in their place, 
FIG. 225. two metal strips, having contact points 

at both ends, as shown, p' n' are sup- 
plied. To these the positive and 
negative poles of a battery are, res 
pectively, attached. The line wire is 
attached to the insulated portion 
p of the vibrating lever p, d, which 
takes the place of the disc d, and is 
acted upon by the collets c and c' 
in the same manner as is that disc in 
the arrangement shown in Figs. 223, 
224. In addition to the foregoing 
changes the ends of the rods h and 11' 
are passed through holes in supports x 
X by which means the motion of the 
lever d is not impeded by the weight 
of those rods. 

The "rider" wheel j, is also con- 
siderably reduced in size and its supporting piece, sp, is reversed. The "ground" is 




WHEATSTONE AUTOMATIC TELEGRAPH. 



301 



FIG, 226. 



connected to the lower portion of the lever d, as shown, the upper and lower portions 

of that lever being insulated from each other. 

This style of transmitter has not been found very well adapted for circuits on 

which high electromotive force is employed, in this country, owing to the sparking 

which takes place at the contact points. There is also, in this form, some difficulty in 

maintaining a line adjustment owing to 
the number of contact points to be con- 
sidered. 

Speed regulator of transmitter. — 
The speed of the clock-work of the Wheat- 
stone transmitter (also of the receiver) i^ 
controlled by a "governor" consisting of 
a regulator contained within the case. 

This apparatus is shown in Figs. 226, 
227, in which a portion of a " fan" f is 
shown extending from the shaft s. At 
the lower end of s a disc d is rigidly 
attached. Below d is i)laced, at right an- 
gles to it a smaller disc d^. The latter 
is mounted on an axle which has its bear- 
ings in a small, movable brass frame b,b, 
whereby it may be moved to the right 
or left. At Its lower edge disc d^ rests 
against a larger disc D2, which latter is 
SPEED REGULATOR. ^'^S^^^^J attachcd to thc shaft s'. s' is di- 

rectly connected with the clock-work 

train, cw. When d- is revolved, d^ in ' ^^^* 

turn, revolves, and causes disc d also to 
revolve. As the disc d revolves, cen- 
trifugal force causes the arms of the fan 
to spread, in which position they encount- 
er the resistance of the air (to an extent 
depending upon the speed) and thus 
retard the speed of the clock-work. 

The speed at which the clock-work 
may run is regulated by the position of 
disc D^ with regard to discs d and d^ and 
this position is adjusted by the movement 
of the bearings bb of the disc d^, from the 
outside of the box, by means of a lever* 
shown at the top of the receiver, 
(Fig. 228.) 

When the disc d^ is in the position 
shown in P'ig. 226, that disc will turn 
quickly because of the large circumfer- speed regulator. 





2,02 AMERICAN TELEGRAPHY. 

ence of D2 as compared with Dj ; while the large circumference of d^ as compared with 
that of the siu'face at which it gears, by friction, with d, gives the latter a comparatively 
rapid motion. When d^ is moved to the left so that it assumes the ];osition indicated in 
Fig, 227, the circumference of r^, so far as disc Dj^ is concerned, is reduced, while that of 
D is increased, with the result that a comparatively rapid motion of D2 imparts but a com- 

FIG, 228, 




WHEATSTONE RECEIVER, 



paratively slow motion to d; thereby reducing the resistance at the fans, and thus per- 
mitting a more rapid movement of the clock-work. 



THE W'HEATSTONE RECEIVER. 



The Wheatstone automatic receiver, or ink recorder, is outlined in Fig. 228. The 
electrical portion of the receiver consists of a polarized relay, not shown in Fig. 



WHEATSTONE AUTOMATIC TELEGRAPHY. 303 

228. Trie mechanical portion consists of machinery devised to move the paper ribbon 
on wnich the ink records are made, as well as that employed in the j^roduction of the 
ink records. The moving force of this machinery is a weight on an endless chain. 
The clock-work and the polarized relay are contained within the frame of the re- 
ceiver. The apparatus shown outside of the frame-work, Fig. 228, will be referred to 
later. 

Fig. 229 shows the devices actually employed in producing the ink records. 
These consist, of a polarized relay pr, an axle x^ and a shaft b, pivoted, with its gear- 
ing,at one end r, and carrying a disc p, outside of the box, at its other end. This disc 
r-ivclves in a groove on the periphery of the wheel w^, but does not touch the latter. 



FIG. 229. 




WHEATSTONE RECEIVER — RECORDING PARTS. 



Wheel w is also placed outside of the box and is rotated by the shaft b, which latter 
is operated by the clock-work vvdthin the box. The lower portion of w revolves in an 
ink-well, v, attached to the frame-work of the receiver, as seen in Fig. 229. The 
paper ribbon passes in proximity to the edge of disc P, but does not touch it. It, at 
times, however, comes so close thereto that it leaves an ink mark on the paper and 
this record is a dot or dash corresponding to the character transmitted from the send in o- 
end. As, by this arrangement, friction is avoided, it will be readily understood that a 
much more sensitive receiving relay may be employed than would be the case other- 
wise. The manner in which the characters are caused to be imprinted on the paper 
will be described 2:>resently. The polarized relay consists of the permanent mao-net 
PM, Fig. 2:19, electro-magnets EM, with two bobbins opposite each other, only one of 
which is shown here; the near bobbin being removed to show the armatures a, a', more 
clearly. Armatures a, a' are rigidly attached to the axle .x',and nt the point of junction 



304 AMERICAN TELEGRAPHY. 

with the axle they fit loosely into a curved notch in the ends of the permanent ma9;net. 
Thus the ends of each armatui-e between the pole pieces of the electro-magnexs are 
" inductively " magnetized to opposite polarity. For instance, that at a would be 
north; that at a' south. The coils of the electro-magnet are so wound that the pole- 
pieces facing one another are of opposite polarity. Thus each armature is attracted 
by one and repelled by the other pole-piece, and it also follows that both armatures 
will tend to move in the same direction when current flows in the coils of tlie elec- 
tro-magnets. The axle x is loosely pivoted on suitable bearings within the box. 
At its upper end it is provided with an extension e, as shown, which does not extend 
outside the box. This extension is given an upward turn at e', suflicient to bring it 
within the range of the shaft b. There is a notch in e' in which b rests very lightly. 

A current intended to record a dot or dash on the paper is termed a " marking '' 
current ; one that is intended to permit a space on the paper, a " spacing " current 
When a marking current is transmitted the armatures move slightly, their motion 
being very limited, in a direction which turns the axle x and, consequently, moves the 
extension e towards the paper, and a dot or dash is recorded. When a spacing cur- 
rent is sent the armatures reverse their positions and the disc is withdrawn from 
proximity to the paper. Thus at each change in the direction of the current, which is 
brought about by the action of the transmitter, the armatures are oscillated, and 
with each oscillation the disc p is either caused to approach or recede from the 
paper. The wheel w, revolving in the ink-well, brings with it sufficient ink to keep 
the disc p well supplied. 

Reverting to Fig. 228. On the frame- work of the box are shown G, the "gover- 
nor " lever, which regulates the speed at which the clock-work, and consequently, the 
paper, will run. v the ink-well, k the roller which, operated from within the box, by 
the clock-work, draws the paper along. The paper in passing the disc p is steadied 
by the rounded projections a^ b. The marking disc p is shown by dotted lines. The 
paper tape is kept in a roll in a receptacle under the receiver. The ink-well is cover- 
ed by a brass top which may be removed by loosening the screw m. The adjustment 
of the armature of the receiver may be accomplished by letting down the 
door, indicated by the screws on the frame of the box, thereby obtaining access 
to the relay. A portion of the door is assumed to be removed to show the contact 
points of that instrument. Two small screws s s' are suitably supported near the 
lower armature of the polarized relay. A small extension, e, from that armature 
plays between these screws, thus limiting the movements of the armatures. 

Adjusting THE WHEATSTONE RELAY. — To adjust the relay the paper should be 
allowed to run at a moderate speed. The extension e is then held loosely against the 
left hand screw s and that screw is moved to the right until the " mark" line appears 
as dots. The screw should then be turned to the left until the marks appear as a 
straight, even line, when another slight turn of the screw should be given, for a mar- 
gin. The extension e is then held in a similar way against screw s' and that screw is 
moved to the left until the marks a23pear as dots, when it should be moved to the 
right until the marks just disappear, when a slightly fm-ther movement should be 
given to s' to the right, also to insure sufficient margin. Care should be taken that 
the marking disc p is not clogged with ink as that would entail a larger space betweeo 



WHEATSTONE AUTOMATIC TELEGRAPH. 



305 



the ends of the screws s s' in adjusting, and an unnecessarily extended motion of the 
armature, with a probable reduction in the speed of reception of signals. 



WHEATSTONE DUPLEX. 



The Wheatstone automatic system in this country is almost invariably worked on 
the polar duplex plan. 

This system as arranged for duplex working is shown theoretically, in Fig. 230. 
In the figure, t is the transmitter, with all but the pole reversing parts omitted, ts is a 



FIG. 230. 



Line^ 




TERMINAL CONNECTIONS WHEATSTONE DUPLEX-THEORY 

switch attached to the frame of the transmitter, used to change from the automatic 
to the manual system, in which latter case an ordinary pole-changer pc, operated 
by a key, k, is employed. When the switch is turned to the left, as at present, the 
automatic transmitter t is in use; when turned to the right, the manual pole-changer 
is placed in circuit. In the former case the circuit starts from e, passes to the 
disc, or transmitter d, thence, via lever z, to the strip i on switch ts, to the negative 
pole of battery b, thence to the strip 3 of the switch, thence to disc d, via lever c, 
thence to the middle strip 2 on the switch, to the polarized relay PR of the receiver, 
where the circuit divides; one portion going to the rheostat R and ground e', the 
other to the line and ground at the distant end. 

G is a differentially wound galvanometer, one of whose coils is in the mam line, 
the other in the artificial line. This instrument is used to balance by, inasmuch as 
the relay is not very accessible. When the balance is obtained the needle will stand 
at zero, if the distant end is to ground. This galvanometer, in the hands of experts, 
is also exceedingly useful for indicatirg, visually, the exact working condition of the 
circuit. It may be repeated here that the differential galvanometer is the equiva- 



3O0 



WHEATSTONE REPEATER. 



lent of a differentially wound relay, its coils being so wound that when currents of 
equal strength flow in them the needle will stand at a zero point. 

The condensers c^ c^ c^ are used, as in other duplexes, to obviate the effects of 
the static induction of the main line. In the very rapid transmission of signals, how- 
ever, a more exact static balance is necessary than in ordinary Morse duplex work- 
ing, and this is obtained by the employment of these additional condensers, each 
with a small resistance in its path. The first condenser has but the resistance of 
R^ to encounter; c^ has that of r^ e^ ^ while c^ has the combined resistances of R^ 
r2 r3 ; the object being to so regulate the charge from the respective condensers that 
they shall equal the near, the middle and the remote portions of the line wire. 

The actual connections now used in a standard Wheatstone duplex set are 
shown in Fig. 231, of which a detailed description is unnecessary. The switch ds 
is a different one from tliat shown in Fig. 230. It serves the purpose of placing the 
line to ground when a balance is desired and also acts as a battery reverser, as may 
be seen by imagining the strips i, 2, 3, of the switch, to be turned to the right; assum- 
ing the strips to be pivoted at the top. The ends of the condensers only are shown. 
The local connections for a sounder are shown at the receiver. This is used when the 
system is being worked simple Morse. The connections are made at the set screws 
Sj s' and extension e, shown in Fig. 228. 

THE WHEATSTONE DUPLEX REPEATER. 

This repeater is operated on the same general principle as the ordinary polar 
duplex repeater, in which the armatures of the polarized relays at the repeating 
station are caused to operate the pole-changer of an opposite set. 

There are, however, several points of difference between the polar duplex repeat- 
er and the Wheatstone duplex repeater, as may be noticed in Fig. 232, which 
is a theoretical diagram of the latter repeater. In that figure pr, pr' are very sen- 
sitive polarized relays, g g' are the differential galvanometers usually employed in 
the Wheatstone automatic system, mb and mb' are main line batteries, each of which 
is grounded in the middle, as shown, (or they may, of course, be two distinct batteries) 
one having its positive pole and the other its negative pole, grounded. In each case, 
the j)oles of the batteries are led to the contact points of the polarized relays, and 
the lever of those relays is connected with the '-'opposite" line wire. Conse- 
quently, as the levers a a are moved from side to side, an opposite pole of the bat- 
tery is alternately placed to the " opposite " lines. 

When the circuits are connected up for repeating "through," the western wire 
passes via r', to the armature lever a of pr and the eastern wire passes via, f, to the 
armature lever a' of pr', thence to the respective main batteries and "ground." The 
arrangement gives the western circuit control of the eastern cu'cuit, and vice versa, 
inasmuch as the western distant station, having control of pr', can reverse the bat- 
tery mb' ; and the eastern distant station, having control of pr, can reverse the battery 
MB. It will thus be seen that the Wheatstone transmitter is dispensed with at the 
repeating station and that the armature levers of the relays pr and pr' are caused to 
act as pole-changers in their stead. In practice these armatures are adjusted very 



3o8 



AMERICAN TELEGRAPHY, 




closely, and necessarily so, on account of the high rate of transmission of signals on 
this system. 

When the circuits are cut " through," as in the figure, the circuit of either side 
may be traced, for instance, from the earth at e, through mb to the armatm-e a of 



WHEATSTONE AUTOMATIC TELEGRAPH. 



309 



pk; thence to the forked wires r' at relay pr', where the circuit divides in the way 
usual to polar duplex circuits, one wire leading to the rheostat r' and " ground," the 
other to tlie western wire. 

When it is desired to separate the circuits for purposes of conversation, " balanc- 
ing", " etc., the 3-point switches s s' are turned, as indicated by the dotted lines. This, 
it will be seen, opens the w'res leading to the armature levers of the polarized relays, 
and puts into circuit the double contact, or pole- changing, keys k, k'. These keys then 
act as pole-changers on their respective circuits ; k reversing the battery mb, and k', 
mb'. 

It is often desirable and essential to know the manner in which signals are pass- 
ing through the repeaters. To obtain this information, readily, the arrangement of 
apparatus at the lower part of the figure is employed. It consists of a polarized re- 
lay PR," a Wheatst)ne receiver wr, a switch h, and high resistance coils l l'. These 
coils have a resistance of about 20,000 ohms each, and the receiver, wr, is wound to 
about 1,000 ohms. These relays and high resistances are tapped on to the main cir- 
cuits as shown at t, t'. 

The strips of the switch h are pivoted in the center and are mechanically joined 
together by the insulating strip x. As shown in the figure, the receiver wr is tapp**^ 
on to the eastern wire ; pr" to the western wire. Should the strip x be thrown ^o 
the left it would connect wr with the western, and pr" with the eastern wire. 

Owing to the high resistance of the, so-called, " leak" resistances l, l', the 



FIG. 233. 




y^- 



presence of the instruments pr and wr is not noticeable in the main circuit, but suffi- 
cient current is diverted from the main line to operate those highly sensitive relays. 

pr" is furnished with a local circuit and sounder and when the speed of trans- 
mission is sufficiently slow the signals are received on the sounder s, but when the 
speed is high the receiver wr' is brought into service. 

The relays in the leak are not differentially wound, hence they are responsive 
to the reversals of polarity of the home battery, but are not responsive to the reversals 
of the distant battery even although it may be undergoing reversals. 

This is due to the very slight change of potential effected by the distant battery 
at the point where the '' leak '' is connected to the line circuit. This statement mav 
be rendered clearer by the aid of Figs. 233 and 233^2:. In these diagrams the re- 



310 



AMERICAN TELEGRAPHY. 



sistance of the line wire is represented by the horizontal line l ; the " slope " of po- 
tential along the wire by the line E. The e. m. r. at each end is assumed to be loo 
volts. In Fig. 233, when the positive battery at a is to the line, and the negative 
pole is connected at b, the fall of potential may be shown by the line e. The leak l' 
is connected at the point indicated and a current flows through it in a positive di- 
rection. When the positive pole of the battery at b is jjlaced to the line, the point 
to which the leak l' is connected at a is raised slightly, as indicated by the dotted 
lines, but the only effect of this is to increase the positive current flowing througli the 
leak from the battery at a. 

When, on the other hand, the negative battery is to the line as at a, Fig. 233a, 



FIG. 233a. 



lOO-^ 




the direction of the current is obviously reversed through the leak, but the only effect 
of a reversal of the distant battery, which may be represented by the dotted lines, 
will be, as before, to increase, in a negative sense, the existing potential at the point 
to which the leak is connected, and thus again to increase current flowing through the 
leak. 

Thus, as stated, the effect of the reversals of the distant battery on the in- 
struments in the leak will only be to slightly increase or diminish the current flowing 
therein, while, at every reversal of the home battery, the direction of the current in 
the leak is completely changed. 

The repeater " set " is provided with the usual duplex outfit of rheostats rr', 
condensers c c' and retarding coils r r'. The batteries are sometimes provided with a 
device for ringing an alarm should they become short-circuited through the relays. 

AoTUAi. CONNECTIONS AVHEATSTONE REPEATER. — The actual conncctious of the 
Wheatstone repeaters, as usually arranged, are shown in Fig. 234. The apparatus is 
generally erected on a large base- board, the binding posts being placed on one side 
of the board and the connecting wires under the board. This arrangement much 
simplifies the setting up of the repeaters, in repeating oflices, as it is only necessary 
to bring the external, main and local batteries and line wires and ground wires, to 
the marked binding posts, when the repeater is, virtually, ready for service. 

In Fig. 234, beginning at the binding jjosts i and 2, on the left hand side. A brass 
hook connects those posts together when the repeaters are working. When it is 
desired to work the apparatus by a separate Wheatstone transmitter the hook is thrown 






Local/ Croec^ic^ 
SO lO 

iz fc 



zo^ 





,o 



^ ZeaA:. 



















1 










ZeaM 



S¥^ 



WHEATSTONK AUTOMATIC REPE 



^Asr 




— CONNFCTIONS — ON ONE BASE-BOARD. 



WHEATSTONE AUTOMATIC TELEGRAPH. 



315 



FIG. 235. 




off, as in the figure, and the transmitter connections are attached to j)OSts i and 2. 

Posts 3 and 4 are arranged for an " extra " condenser, if one shoukl be necessary for 

a proper balance. In that case, wires from the condenser are led to posts 3 and 4, 

when the condenser will be found to be in the 
proper place, that is, practically as shown in 
Fig. 230. Post 5 is connected with the main 
line wire, in this case assumed to be the western 
wire. Posts 6 and 7 are connected, respectively, 
to the zinc and copper poles of the main line 
battery. Posts 8 and 9 to the zinc and copper 
poles of the local battery of the sounder s of the 
leak relay. Posts 10 and 11 are connected 
to the ground. Posts 12 and 13 are connected 
with the zinc and copper poles of the local 
battery of the sounder s' of the leak receiver. 
Posts 14 and 15 are connected, respectively, with 
the zinc and copper poles of the " east " main 
line battery. Post 16 is connected with the 
eastern line wire. Posts 17 and 18 are provided 
for an extra, or third, condenser. Posts 19 and 20 
are provided for the insertion of a transmitter 

in the same manner as posts i and 2, described. 

It will be seen that the instruments of the western set are a duplicate of those of 

the eastern set. The leak relav, 

, , 1 . "^ FIG. 236. 

the leak receiver (p r" and wr of 
Fig. 232) and the switch x are 
common to both sets, eg and wc 
are boxes, each containing 2 con- 
densers arranged in one box for 
compactness. The leak resistances 
are contained in boxes as marked 
and are furnished with switches by 
which the coils may be '' opened " 
when required, eg, wg are differ- 
ential galvanometers, wx and ex 
are resistance boxes containing 
separate coils for the artificial line 
and condenser resistances. These 
rheostats are cf the ^/a/ pattern 
and are shown separately in Fig. 
237, WK and EK are small 
base boards on which are the keys 
used for conversation, and a 3-point switch for separating the western and eastern 
sets. This key and switch correspond to k k' and s s', Fig. 232. sg and sg' are 
metal segments to which the ground wives are attached. l>y means of the plugs, 




WHEATSTONE REPEATER RELAV. 



3i6 



AMERICAN TELEGRAPHY. 



shown inserted in the center, the sets may be speedily disconnected from the 
ground. 

WR and EE, Fig. 234, are the Wheatstone "repeater" relays. 



FIG. 237. 




DIAL RHEOSTAT. 



The routes of the circuits, when arranged for working " through," may be read- 
ily traced by the small figures i-|-; 1 — ; 2-f-, 2 — ; etc., from the main battery posts, 
up to the split, or fork, that is the junction of the main and artificial wires, whence 
the circuits may be further traced by the numbers i3al, 13ml, etc., referring to 
"main line " and "artificial line," as will be seen on examination. 

The arrangement of two condensers in one box, just referred to, is shown sep- 



WHEATSTONE AUTOMATIC TELEGRAPH. 



317 



arately in Fig. 235. In tliat figure the brass strip is in two parts, s, s, each part 
including a certain number of plates. Between the two strips the wires lead to a 
resistance which may be considered as corresponding to r^ i^ pig. 230. 

Wheatstone repeater relay. — It is obvious that the ''repeating" relays used 
in the Wheatstone automatic repeaters must be both sensitive and easy of adjust- 
ment. Such a relay is that shown in top view in Fig. 236. It is a polarized relay, 
wound for duplex working, pm is the permanent magnet, which magnetizes the ar- 
mature A of the relay in the same manner as does the permanent magnet of the " re- 
ceiver " relay. The tops of the two bobbins b b' are shown. The core of each mag- 
net is supplied with pole-pieces p p' between which the armature vibrates. The arma- 
ture is adjusted by means of the movable contact screws me, me'. The play of the 

FIG. 238. FIG. 239. 

6 6' 





0- ;6r \ 

1 2 3 ^\^ 



armature which is necessarily very small, is regulated by the distance between the 
contact points c, c'. These contact screws move in the brass supports s, s'. This 
relay is adjusted for a balance in, practically, the same way as the ordinary polar 
duplex relay. The bobbins and armature are contained within a cylindrical brass 
frame, except near the top, where a tight-fitting glass cover is attached to exclude 
dust, etc. The ends of the contact screws extend outside of the frame and tlius are 
readily accessible for adjustment of the relay. 

Dial rheostat. — The adjustable rheostat generally used in the Wheatstone au- 
tomatic system in this country, as well as in Europe, is of the dial pattern. It is 
shown, theoretically, in Fig. 237. h and h' are metal hands pivoted iu the center 
of the dial like the hands of a clock, and movable in either direction. Around the 
dial are metal discs on any one of which an end of h and h' may rest. The termi- 
nals of the resistance coils are brought to these discs, as shown. The external con- 
nections are made at the binding posts bs, bs'. 

The sum of the resistance coils on the left hand half of the dial amounts to 400 
ohms, as indicated by figures, each coil being wound to 40 ohms. That of the ceils 
on the right, 4,000 ohms, each coil being wound to 400 ohms. There is also an extiu 




3l8 AMERICAN TELEGRAPHY. 

coil EC, on the left of the dial which may be added to the circuit, when required, hy 
removing plug p. 

If, as in the figure, the hand h' rests on the 2,000 ohm disc, and the hand h', on 
the 120 ohm disc, there will be a total resistance of 2,120 ohms in circuit, as may 
be found by tracing the route, starting from the 2,000 ohm disc, from which the cir- 
cuit then passes through the hands h' h and thence to the 120 ohm disc, thence to, 
but not through the extra coil ec, as it is short-circuited by the plug p, to the post 

BS. 

FIG. 240. The total resistance of 

2^/7 QOO such a box as that shown in 

the figure would be 8,400 
ohms, but, it is, of course, 
net imperative that this 
particular resistance should 
be adhered to. This form 
<COO /Cc/i/ of rheostat is very conven- 

ient in balancing as it is 

only necessary to slip the hands around from disc to disc in any desired direction 

until a balance is obtained. 

Wheatstone polaeized ee- ^^^* ^"^^ "' 

I.AY. — The actual winding ^-^^-322^ 

and arrangement of the 

Wheatstone relay is indicated 

in Figs. 238, 239. 

This relay, as already 

Btated, is composed of two 

separate, soft iron bars b, b'. 

Two coils of 200 ohms each 

are wound on each bar, the 

terminals of which coils are 

brought to binding posts as shown. The winding is arranged to cause tlie poles that 

face each other, of the magnets, to be of opposite polarity. For example, a current 

which would tend to make one end, b^ of bar b, a south pole, would make the end b' 

of b', a north pole, and contrariwise. The manner iu which the armature of the relay 

is placed between these ])oles has already been shown. 

In " single "' working the terminals of the coils are frequently arranged so as to 

permit placing portions of the coils in series or in multiple, for the purpose of min- 

imizing the effects of "self-induction" which, as has been shown, conduce to slower 

signaling, {see Self Induction.) * 

* Placing the coils in multiple effects this result. mainW. perhaps, by putting the electromotive forces of self-induction 
in parallel instead of in series, as indicated in Figs. 240 and"^ 240a. It also decreases the ampere turns of the relay {See page 
66), upon which, among other things, the self-induction depends. For example; if with one set of coils in series there are 
500 turns of wire, and on the line .1 ampere, the ampere turns will be 50. Placing this set of coils in multiple gives, say, 
two sets of coils, each with 250 turns and each now carrving .05 ampere (assuming that the reduced resistance of the coils in 
multiple will not materially vary the line current), which gives 12.5 ampere turns for each coil and a total for both of 25 
ampere turns. Of course, where a large number of relays are on one circuit {See other page), a change to the multiple 
winding might be expected to materially reduce the total resistance. 




WHEATSTONE AUTOMATIC TELEGRAPH. 3^9 

To connect the coils ill multiple the binding posts i, 2 and 3, 4 are joined by 
metal strips, as in Fig. 238. To connect in series the posts 2, 3, are joined, as in Fig. 
239. When connected in multiple the joint resistance of the coils is 50 ohms. When 
ill series the resistance of the coils from post i to post 4 is 200 ohms. When arranged 
ill series, or more correctly, in this instance, multiple-series, the coils are connected, 
virtually as shown theoretically in Fig. 240; when arranged in multiple they are 
connected virtually as in Fig. 240^. 

The resort to the multiple connections is more essential in the case of " single" 
wire working, especially when a large number of relays are in the circuit, inasmuch 
as the total " extra " current of the coils in series would materially affect the speed 
of signaling. 

C0XDE]S^SER ^'^ EXTRA currei^t" xeutralizer. — Another device for diminishing 
retardation due to the " extra current " of self induction employed in single working in 
the Wheatstone automatic system, consists of a resistance in the main line circuit 

shuntinai: the terminals of a 

FIG. 241. ^ 

^^^^^^^^^^ condenser, as outlined in 

^^^ ^ ^ _ , ..^^p.^^>^^popr > Fig. 241, in which pr may 

jpj^ -^-^ A represent the polarized relay ; 

R a resistance wound upon 
itself to prevent magnetic 
effects, and c a condenser. 



c 



The object, of course, in using this resistance is to get the necessary difference of 
potentials at the terminals of the condenser. 

As the current of discharge from a condenser is in the opposite direction to that 
set up by the charging electromotive force it will be understood that the effect of the 
current of discharge from the condenser will be to neutralize the current of self-in- 
duction in the relay at the moment the circuit opens. This effect is indicated by the 
arrows in opposite directions in the figure. 

This device has been found to very materially increase the speed of transmission. 



BALANCING AND ADJUSTING WHEATSTONE APPARATUS, ETC. 

In taking a balance on the Wheatstone duplex after the distant station has 
grounded, dot slowly on the key and alter the resistance in the rheostat until the 
galvanometer is not affected. Then, to get a static balance, after the distant end has 
cut in, run an alphabet or piece of old slip through the transmitter, at the same time 
having the distant office run his transmitter, and adjust the static compensating con- 
densers and the retarding coils connected with them, until no effect is noticeable on 
the signals from distant end. 

The part of the Wheatstone automatic apparatus requiring most care is the 
transmitter, which, to do successful work should be given close attention. The plat- 
inum pins and plates on the battery arms of the levers and disc d should be kepj 



320 AMERICAN TELEGRAPHY. 

thoroughly clean, as any imperfections of contact will unsteady the outgoing cur- 
rents and cause signals t > drop at the distant end. The slots in the brass extension 
from the framework of the receiver, which admit the star- wheel and the vertical rods, 
should be cleaned out occasionally, as they get filled up with paper dust. Should the 
distant offi'3e, or repeater station, complain of signals droj^ping, first inquire if there 
is any indication of " bias. '' A bias will be indicated by the needle of the differ- 
ential galvanometer at the receiving station ; that is, it will hang to one side or the 
other, of zero; or the bias may be indicated by " lines. " or " drops," as the case may 
be, on the paper tape of the receiver. The bias is due to uneven duration of contacts 
at the disc of the transmitter. When the transmitter is working at high speed and 
the duration of contacts is practically uniform, the pulsations of current will, owing 
to their rapidity and uniformity of strength, not noticeably vibrate the needle of 
the galvanometer, for the simple reason that the inertia of the needle, that is, its dis- 
position to remain at rest, is not overcome — or, in other words, before it can respond 
to the impulse to move in one direction it is met with an equal impulse to move in 
the other direction. But, when, by reason of an uneven contact at the transmitter, 
the current from one pole of the battery is of longer duration than that of the other 
pole, the needle obeys the more prolonged impulse and tends to hang to one side of 
zero, as before stated. 

If the distant end reports a bias it can generally be remedied by moving the top 
collet to the right for marking, and to the left for spacing, or by moving the collet on 
the bottom rod, to the left for marking, and to the right for spacing. This is, of course, 
assuming that all transmitters are connected up alike which, as a rule, is the case. 
The collets can be adjusted by moving them forward or backward, on their respective 
rods or shafts, and to obtain their correct position a " blank " slip should be passed 
through the transmitter, when, if the collets are in correct position, they will not 
move the disc of the pole-changer. The collets are kept immovable after adjustment 
by tightening up the adjoining set screws on the collet rods. 

If complaint of bias is still made, although reversals be properly received at the 
distant end, and if the home perforated slip is in gauge, that is, with the star-wheel, 
it is possible that the upright rods of the rocking beam may not be in proper 
position. 

If your signals drop at the distant station, the stop screws, or pins, may be too far 
to the left, and one or both should be worked back a little to the right. Should the 
^//'j-/^;?/ j/i/Z/f^/z complain of receiving " lines " or "markings," the stop screws should 
be moved to the left ; or the jockey roller may require a little adjustment. The said 
dropping of signals may also be due to too much pressure of roller. If the signals 
run to lines the jockey roller may require letting down somewhat. Sometimes the 
springs s, s, Fig. 224, which push the collet rods h, h' forward, may require strength- 
ening. 

To all of the Wheatstone apparatus, as in the case of the quadruplex apparatus, 
and, perhaps, more so, on account of the greater speed at which the former is 
worked, as well as the greater complication of the machinery, much attention should 
be paid. The contact points especially should be kept bright and free from dust, etc., 
and the local and main batteries should be kept up to a high standard of excellence. 



AUTOMATIC TELEGRAPHY. 



321 



The E. M. F. found necessary on Wheatstone duplex circuits of say 400 to 500 
miles is from 150 to 175 volts of each polarity. This system is still largely used in 
Europe (1903), but its employment in this country has been confined to the circuits 
of the Western Union Telegraph Co. Tne speed at which signals are transmitted 
over these long circuits varies with the conductivity and general conditions of the 
wire. Between New York and Chicago, a distance of 1000 miles, with repeaters at 
Buffalo, less than midway, a speed of 150 to 200 words in each direction is main- 
tained. 

The arrangement shown in Fig. 241 is used as stated, in single automatic work- 
ing for the purpose of diminishing retardation due to induction. As it may be 
assumed that two currents cannot flow in the same direction in the same portion of a 
wire simultaneously, it is perhaps better to consider that in the figure, at the moment 
of cessation of the current due to the battery or dynamo, the E. M. F. due to the induc- 
tance of the relay and the E. M. F. due to the previous charge of the condenser 
oppose each other, and thereby prevent an extra current, or it is possible that the 
condenser performs its function of facilitatiiig signaling, not only by neutralizing, 
but also by over-riding the extra current of the relay. In Fig. 241^^ is outlined 
the method of arranging the extra current condenser and also what are termed 

signaling condensers in automatic du- 
FIG 241a. plex working on mixed aerial and com- 

paratively short submarine cables, as 
between London and Paris, e is the 
extra current condenser, which, it is 
seen, is' in a bridge wire; r r are the 
arms of the bridge. This is virtually 
the F. W. Jones condenser arrangement 
for duplex telegraphy, which corresponds 
to the Smith arrangement with the thii-d 
coil omitted, which is fully described 
on page 204. s s are the signaling 
condensers, which are placed around 
the bridge arms and the relay coils IVL, as shown. The office of the signaling con- 
densers, acearding to some authorities, is to neutralize the return static current from 
the cable, by which it is perhaps meant that the signaling condensers in discharging 
assist in neutralizing or "wiping " out the previous charge of the cable, and in charging 
assist in the prompt recharging of the line. It would seem also that the tendency 
of the condensers s s as thus disposed around the coils of relay m would be in dis- 
charging (that is, that portion of the discharge which would take this route) to 
prolong the extra current in the relay (see page 342), which in practice is the case, 
but this effect is offset by additional capacity in the condenser e. It is evident, on 
the other hand, that these condensers should facilitate the transmission of signals, 
inasmuch as they in effect cut out of the circuit the resistance coils r r and the 
respective coils of the relay, or, in other words, they tend to ''switch" the rapid 
pulsatory currents past those coils (it being known that electromagnets are. as C. ~'^\ 
Varley pointed out, partially '^opaque" to such currents), the ensuing diminution 
of received currents being compensated by condenser e. The use of this arrarire- 




22 1^ AMERICAN TELEGRAPHY, 

ment has been found to increase the speed on the circuits referred to about loo per 
cent. Preece and Sivewright's " Telegraphy ^^ gives figures showing that on 
the London and Amsterdam circuit, consisting of 130 miles aerial wire on the 
British side, then 130 miles of cable and 20 miles aerial in Holland, without the 
signaling condensers the speed of working from London to Amsterdam is 48 words 
per minute, while 68 words per minute may be transmitted from Amsterdam to 
London, this difference being attributed to the nearness of the cable to Amsterdam. 
With the signaling condensers the speed of working on the same circuit is increased 
to 116 words per minute in each direction. 

In the figure, u is the artificial line resistance. K^ r' r^ and condensers c c c 
correspond to those used in compensating for the static capacity of the line in 
automatic duplex working. {See Fig. 230.) b is the usual battery or dynamo 
source of E. M. F. 



THE STEVENS-WHEATSTONE PERFORATOR AND TRANSMITTER. 

This is a device which is attached to a Wheatstone receiver in such a way that 
short and long dashes are perforated in a straight line on a paper strip instead of 
the usual ink records. The message can then be read by sight or it may be passed 
through a transmitter and received by sound or transmitted on to another station. 
The relay is practically similar to the regular Wheatstone receiver, except that a 
forked lever takes the place of the extension which in the latter carries the marking 
disc. The fork projects over a small bolt on the surface of which there is a small 
pin with v/hich the fork engages. The punching devices consist of a vertical rod or 
plunger continuously moving up and down in suitable guides at a rapid rate by 
connection at its upper end with a crank-pin operated by a motor. A small foot- 
piece at the lower end of this rod moves up and down with it. The punch proper 
is also arranged vertically, its head being slightly to one side of and above the 
lower end of the plunger. In the head of the puncher there is a small vertical 
slot, the length of which is equal to the up-and-down motion of the plunger. 
The foot-piece works in this slot. The small bolt referred to is moved into and 
out of this slot through a hole in the side of the head of the puncher by the 
engagement of its pin with the forked lever. A marking current pushes the bolt 
into the slot, thereby shortening the length of the slot, with the result that the 
foot-piece depresses the cutter of the puncher through and withdraws it from the 
paper strip at a high rate of speed, a short hole or slot being punched for a dot, a 
longer hole for a dash. A spacing current withdraws the bolt from the slot, and at 
such times the puncher is passive. 

The transmitter for retransmitting the messages thus prepared is more or less 
analogous to that shown on page 72, one end of a lever l being allowed to pass 
through the perforations in the strip, the other end playing between contacts which 
are connected to positive and negative poles of a battery or dynamo, the Hne being 
connected to the lever. A speed of over 180 words per minute has been attained 
by this device on circuits of about 250 to 300 miles in length in Great Britain. 



AUTOMATIC TELEGRAPHY. 



THE DELANY RAPID AUTOMATIC TELEGRAPH. 



321^ 



In the Delany system a Morse key operates a punching-machine which cuts 
holes, representing dots and dashes, in a paper strip. Holes are punched in two 
rows on the strip, Fig. 241^5. For dots the holes are punched slightly diagonally, 
as for E in the figure; for daslies the holes are punched considerably moi-e aslant, as 
for T in the figure, like the holes for dashes in the Wheatstone perforated paper, 
page 297. In the operation of the punching-macbine the closing of the Morse key 
causes a punching-magnet to perforate the upper hole, and the opening of the key 
causes another magnet to perforate a lower hole in the paper; and between these 
operations the paper is fed on, the longitudinal space between an upper and lower 
hole depending on the length of time the key is held closed, the necessary mechanism 
to reguhite the amount of paper fed for dots, dashes, and spaces being provided. It 
will be obvious that an operator at one station may in this way prepare the paper 
by a punching machine at a distant station. 

The double-current method is em})l()yed in this system. In the transmitter four 
brushes, Fig. 241^, are employed, two upper and two lower, which tend to press 

FIG. 24I<^. FIG. 241^:. 



against each other as indicated. Two of these brushes rest on the top of the paper 
strip, two below it. The positive pole of a battery is connected, as srhown, to the 
brush opposite the upper row of holes in the paper strip; a negative pole to the 
brush opposite the lower row of holes. In the receiver three needles are used: the 
two outer ones are of platinum and are connected to the earth; the middle needle is 
of iron and is connected to line L, Fig. 241c. The base of the chemical solution 
with which the receiving-paper is dampened is prussiate of potash. A current 
in a positive direction leaves a mark on the paper under the iron needle; the 
platinum needles are not attacked. Eeference has already been made to the effect 
of the static capacity of the line in producing tailings on chemically prepared paper 
(page 288). In the present system advantag-e is taken of this effect in the arrange- 
ment of the perforated holes for dots and dashes at the transmitter. In the 
operation of making a dot, when the upper or positive brush meets a hole and 
thereby makes contact with the brush under it, and completes the circuit, a positive 
current is sent to line. Almost immediately the lower or negative brush completes 
the circuit, although there has been a moment of no battery to line while the pa]ter 
intervened. This negative potential clears the Hue of positive current, but in tlio 
meantime a dot had been recorded on the receiving-strip. When a dash is t«^ be 



322 



AMERICAN TELEGRAPHY 



sent the greater space of paper between the upper and lower holes allows the tailing 
current to exist longer before it is followed by the clearing-out current, and a dash 
is recorded on the chemically prepared receiving-strip. As the " space" character is 
always preceded by a clearing-out current, it follows that no current, or at most only 
negative tailings, which do not mark, will be on the line when a space is to be indicated. 
The advantages of the Delany automatic system are somewhat akin to those of 
the Phillips- Weiny automatic telegraph, page 72, but a much higher speed is obtain- 
able with the chemical method of transmission, some data on which have already been 
given, page 294. Of course it will be understood also, from what has been said, 
that the perforated strip may be used when desired to transmit signals at a rate 
receivable by Morse operators by sound. The receiving machine of the Delany 
system is self-starting and self-stopping [see page 373 for examples), and also stops 
automatically when the transmitting tape passes out of the sending machine. 



AUTOMATIC FAC-SIMILE TELEGRAPHY. 

Fac-simile telegraphy relates to the transmission and reproduction, at a distance, 
of characters, symbols, or pictures. 

There are tw^o general methods by which this has been accomplished, namely, an 
electro-chemical and an electro-magnetic method. 

In electro-chemical methods the characters, etc., to be transmitted are, as a 
rule, prepared, in some form of insulating ink, \\\)0\\ a metallic base, such as a strip of 
tin-foil. At the receiving station a strip of chemically prepared paper, cor- 
responding in dimensions with that of the tin foil, is used. The un-foil and paper 
strips are respectively connected in a circuit, practically as are the paper strips of the 
chemical automatic systems, already described, and means are provided whereby_ the 
characters are reproduced on the prepared paper by the electrical decomposition of 
the components of the solution in which the receiving paper strip had been pre • 
viously immersed. 

In electro-magnetic methods the characters to be transmitted are sometimes em- 
bossed on card-board, which is then placed on a suitable cylinder. A blank card is 
placed on a similar cylinder at a receiving station. The cylinders at both ends of 
the circuit are, by any suitable means, synchronously rotated, spirally. A light lever, 
controlling the contact points of a circuit, is placed over the transmitting card. 
As the cylinder is rotated and, at the same time, moved laterally, the lever is raised 
and low^ered as it passes over the embossings, with the result that, as it does so, the 
circuit is alternately made and broken. These makes and breaks of the circuit at 
the transmitter are caused to actuate a pen supplied with ink, attached to the arma- 
ture of an electro-magnet in the circuit at the receiving station ; the arrangement of 
the lever being such that when the circuit is broken the pen rests on the card on the 
receiving cylinder; while, when the circuit is closed, the pen is lifted from the card. 
Consequently, there is reproduced, in ink, on the receiving card, by these makes and 
breaks, a practical fac-simile of the embossings on the transmitting card. The em- 
bossings on the latter card may be made by a thick ink traced on the paper by a 
suitable pen or brush. Evidently, the arrangement described could be reversed, and 



FAC-SIMILE TELEGRAPHY. 



323 



the openings and closings of the circuit be caused by holes, depressions or " etchings " 
in the paper. \ 

THE DENISON FAC-SIMILE TELEGRAPH SYSTEM. 

An electro-chemical fac-simile system now employed in this country is 
shown theoretically in Fig. 242, in which t is the transmitter, k, the receiver. 'Qiese 
instruments, it is seen, are nearly similar in general construction. Each consists of a 
polarized relay pe, pe', the function of each of which is to cause the vibration of the 
arms a, a', which are attached, as indicated, to the armatures of the respective re- 

FIG. 242. 




DENISON FAC-SIMILE TELEGRAPH. 



lays. The amplitude of the vibration of the arms is regulated by the stop screws* s, s ; 
s' s'. These relays are in a common circuit c', in which circuit rapid reversals of 
polarity are produced by a ''generatcr " d; in this case a small alternating current 
dynamo machine, driven by any suitable motor. Being in the same circuit the relays 
will cause their armatures and, consequently, the long arms, a, a/ to vibrate in unison. 

At the transmitter, r is a strip of tin-foil on which characters are traced with 
insulating ink. The foil is caused to pass over and through a suitable roller and guide. 
The chemically prepared paper at the receiver is also passed over a roller and a plat- 
inum plate r'. 

A circuit c is provided for the transmission and reproduction of the charactei'S. 
The circuit ])asses from earth at t to the earth at k. A small contact needle n is 
arranged on the arm a' of the transmitter, as shown. This needle normally rests on 
the tin-foil. A stylus, or pen n', is similarly arranged on the arm a' of the receiver. 
Delicate spiral springs, suitably arranged, hokl the needle and pen snugly against the 
tin-foil and paper. The transmitting battery, b, at t, is normally short-circuited by 
the arm a and the tin-foil, via the needle w; consequently, at sucli a time, no current 
passes to line. When, however, tlie, needle n rests on, or passes over, the insuhited 
.nk, the short-circuit is broken and a record is made on tlie prepared paper at the re- 



323^ 



DENISON FAC-SIMILE TELEGRAPH. 



ceiver. The operation of the apparatus will be readily understood. At a given sig- 
nal the transmitter and receiver are set in motion. As before stated the arms are 
caused to vibrate synchronously. (The vibrations occur at the rate of about 1,500, per 
minute.) At the same time the tin-foil at the transmitter and the paper at the re- 
ceiver are caused to move forward at a practically equal rate of speed. Since current 
will only flow in the circuit c when the needle of the transmitter is passing over the 
insulating ink, and as the record is only made at the receiver when current is flowing, 
9.nd, further, as the pens at t and e are always at corresponding points of the tin -foil 

FIG. 242 a. 




and paper, respectively, it results that there will be reproduced on the chemical paper 
a fac-simile of the characters placed on the tin-foil. 

In Fig. 242^ the transmitter t and receiver e are shown as, in practice, they are 
combined on one base, h is a switch which is normally in a middle position as re- 
gards the slot ill which it moves. "VVlien in this position an electric bell is included 
in the circuit of the relays. The act of depressing the handle of h, at either end, 
by throwing in the battery, taps the bell, indicating that a message is to be sent, 
w^hereupon the distant station lifts up his switch, thereby placing his receiver in the 
circuit. When desired the bell may be operated for code signaling in the trans- 
mission of short messages. 



THE PALMER-MILLS ELECTROGRAPH. 



This is an electromagnetic system by means of which messages or pictures may 
be transmitted. It employs a transmitting and receiving cylinder practically similar 
to those already described, also a transmitting stylus and receiving pen. The method 
of preparing the message or picture for transmission and other details are, however, 
difl'erent. In this system the message or picture to be transmitted is, up to a certain 



THE PALMER-MILLS ELECTROGRAPH. 



323'^ 



point, prepared in the same manner as a half-tone, on a zinc plate, but in the final 
preparation the etchings in the zinc are filled with an insulating wax, thus proyiding 
a smooth combined insulating and conducting surface, over which the transmitting 
stylus travels. The zinc plate is then bent over the cylinder and locked in position. 
It takes about twenty-five minutes to prepare the plate. The transmitting and receiv- 
ing cylinders are revolved synchronously by suitable motors at the rate of about 40 
revolutions per minute, and the stylus and receiving pen and its magnet are moved 
])urallel with the axis of the cylinder by screws which have a pitch of 40 or 80 
threads to the inch, as may be selected. Synchronism of rotation between the 
transmitting and receiving cylinders is maintained by impulses sent at certain parts 
of each revolution of the transmitting cylinder, at which moment the receiving-pen 
magnet is cut out. The receiving cylinder being set to revolve slightly faster than 
the transmitting cylinder, these synchi'onizing impulses operate magnets which 
ap[)ly a small friction-brake to the fly-wheel of the receiving cylinder. From the 
immediately preceding descriptions of other facsimile systems, the operation of this 
system will be readily understood without further explanation, it being understood 
that a suitable paper is employed on the receiving cylinder, the pen of which records 
at the rate of about 80 dots per second. 



THE POLLAK-VIRAG AUTOMATIC TELEGRAPH SYSTEM. 

This system employs a perforated jiaper tape somewhat similar to the Wheat- 
stone, the holes on one side of the paper transmitting dots, those on the other side, 
dashes. This paper passes between two metal bruslies and a metal cylinder. One 
brush sends curi-ent of one polarity, say, positive; the other sends negative polarity 
to the line. Two wires are used between stations. The receiver is a telephone, the 
diaphragm of which is set into oscillation by the current pulsations, the direction of 
the oscillation corresponding to the polarity of the current transmitted. These 
oscillations are communicated to a small mirror, which is attached to the diaphragm 
by a metal rod in such a way as to largely amplify the motion of the mirror; a 



Fig. 242<^. 



Fig, 242c, 




p. -m 



TRANSMITTING AND RECEIVING CIRCUITS. 



RECEIVING apparatus; 



condenser is placed around the telephone to prolong the duration of the current 
impulses and to steady the oscillation of the mirror. A snudl incandescent lamp is 
caused to throw .a beam of light on the mirror, which beam is reflected by the 
mirror through a slot in a cylinder within which is contained a moving roll of 
sensitized paper. When the system is in ojieration the beam or pencil of light 
is moved to the right or left, depending on the direction of the current, and a record 



is produced on the sensitized paper, which, when developed, resembles the r 
made by the siphon recorder. 'J'his system has been tested between Bud 
and Viennsi, a speed of 1500 words per minute being reported, on a metallic circuit 
400 miles in length having a resistance of 4000 oh ink See Fio-s. 242I), 24 jr. 



ecord 
[I pest 



CHAPTER XIX. 



WRITING TELEGRAPH SYSTEMS. 

Writing, or autographic, telegraph systems may be distinguished from automatic 
fac-simile telegraph systems in that the former systems electrically transmit and record 
fac-similes of letters, or characters, while they are being formed by the stylus, or pen of 
the transmitter, in the hands of an operator. Ordinarily, autograph telegraph systems 



FIG, 243. 



Fig* 244. 




T 





ROBERTSON RECEIVER. 



ROBERTSON TRANSMITTER. 



simply reproduce in fac-simile the writings or sketches which have been previously pre- 
})ared on a conducting surface; as in the case of the Denison fac-simile telegraph, herein 
described. 

The first to invent a telegraph system which would reproduce electrically the 
hand-writing of the operator, simultaneously with the writing, was Mr. E. A. Cowper, 
of England. 

The principle of operation of tlie writing telegraph is that of " compounding the 
movements of a point, in two directions, the one at an angle to the other, the actual 
movement of the point being the resultant of the two movements'.' {See Galvanomet- 
ers). 

The operation of the receiving pen depends, primarily, upon variations of the mag- 

324 



WRITING TELEGRAPH SYSTEMS. 325 

ft»etic strength of two electro-magnets, placed at right angles to each other; which 
variations produce changes in their magnetic fields, in which an armature to wliicli the 
receiving pen is attached, is placed, and to which changes the armature is free to re- 
spond. Each of said magnets is, in practice, placed in a separate circuit. The vari- 
ation of the current strength in the circuits which effects the fluctuations in the mag- 
netic fields, is brought about by means of a stylus which, when moved, as in the act of 
writing with an ordinary pen, causes variations in the resistance of the respective cir- 
cuits. The transmitter employed by Mr. Cowper consisted of a stylus which was caused 
to slide over contact points, thereby cutting in or cutting out resistance coils. 

Subsequently, Mr. J. Hart Robertson devised a transmitter which, when moved as 
in writing, varied the resistance of the circuit by varying the pressure on two series of 
carbon discs, each of which series was in a separate circuit. 

This arrangement was adopted with a view to obtaining a more uniform and 
gradual variation in the resistance of the circuits than had previously been obtained, 
and was found to work successfully in practice. The receiver now used by the Writing 
Telegraph Company, now to be described, is also due to Mr. Robertson. 

WRITING TELEGRAPH COMPANY SYSTEM. 

The Robertson transmitter and receiver are shown in Fig's. 243 and 244. In 
practice these instruments are enclosed in one box. 

THE ROBERTSON TRANSMITTER. — This transmitter, T in Fig. 243, consists of two se- 
ries of thin discs of carbon placed at right angles to each other. Each series is made 
up of 30 discs, each disc one-half inch in diameter, and one-twentieth of an inch thick, 
placed side by side, within a hard rubber receptacle c or c'. r is a vertical rod which 
is supported at its lower end on a flexible wire. Apertures are made in the hard rub- 
ber receptacles througli which an end of each series of discs may be reached by short 
projections from the rod r. The rod r extends upwards and passes through an open- 
ing in the cover of the box, not shown in the figure, where it is flexibly connected to 
an attachment resembling an ordinary stylus. The opening is of such a size as to 
permit only a limited motion of the point of the stylus in any direction. Any motion 
cf the rod r causes a variation in the degree of pressure of the projections against the 
ends of the discs, the pressure increasing according to the extent of the motion towards 
the discs. The normal pressure of each series of discs is adjusted by screws x x'. 

THE ROBERTSON RECEIVER. — The reccivcr, Fig. 244, consists of two electro-magnets 
M, m', also placed at right angles to each other. Each magnet has an armature a, a', 
of peculiar construction. The armatures are magnetically insulated from each other, 
being joined together by a brass strip. These armatures are supported by the rod r', 
which latter rests on a flexible wire, as shown. This rod also rises through an opening 
in the cover of the box and carries at its top aloosely pivoted, hollow cylinder p, as 
shown. This cylinder holds an ink which supplies the pen at the lower end of the cyl- 
inder. The pen rests loosely on a strip of paper. The rod r' carries, about midway, an 
inverted thimble t', which moves freely in a pot c containing glycerine. The pot is 
supported by the framework. The function of this device is to steady the motion of 
the rod and, consequently, the pen. Without this device the writing is found to be 
wavering. The operation of the transmitter and receiver will be described presently. 



326 



AMERICAN TELECxRAPHY. 



ROBERTSON WRITING TELEGRAPH — CONNECTIONS. 

A theoretic diagram of this writing telegraph system is given in Fig. 245. d, d' 
are the series of carbon discs of the transmitter t. m m' are the electro-magnets of the 
receiver. The series of discs d is in circuit with the magnet m; the series d', with 
the magnet m'. Each circuit has a battery b, b'. The vertical rod of the transmitter is 
indicated by r; the projections which reach to the ends of the carbon discs by e <?'; 
the rod and armatures of the receiver by r' and a a'. 

It is well known that the electrical resistance of carbon varies under pressure, the 
resistance decreasing as the pressure is increased. This fact, as previously remarked, 
is availed of in this system, and the arrangement of the discs just described is chosen 
to obtain the greatest variation with a minimum of pressure. Each disc of each series 

FIG. 245. 




C 



11 




has a resistance, under a pressure of 8 lbs., of about 2 ohms. 

The two circuits employed in this system are practically separate from each 
other. 

When the apparatus is at rest the projections e e' on the rod r of the transmitter 
(Fig 243) press equally against their respective discs. Consequently an equal current 
flows through both circuits and the magnets at the receiver are equally attracted. 
When the pressure is increased on each series of discs, equally, the increase of curi-t- nt 
in each circuit is uniform, and the attractive force of each magnet moves the armature 
forward diagonally between them. A uniform decrease of pressure permits an oppo- 
site backward motion of the armature. When one projection, say, e is caused to press 
more strongly against its disc d, by reason of a particular movement of the handle of 
the transmitter, the resistance of its circuit c is decreased, while tliat of the other cir- 
cuit c' is augmented by the increase of resistance due to a reduced pressure on the discs 
d'. This produces a variation in the current strength and causes an increased attrac- 
tion of the armature a of the receiver, which armature is attrar-,ted towards its magnet, 
carrying with it the rod r' and its pen ; but as the magnet ii' still continues to exert 
some attraction on armature a' the motion of the rod will be more or less in a cuiwe, 
depending on the attractive power of the respective magnets. 



ETHERIDGE TRANSMITTER. 



327 



FIG. 247. 



lu the act of transmitting a message by this system, the sender takes 
riold of the handle of the transmitter and proceeds to write in the ordinary way, except 
mat the letters are, as it were, made one over the other. The movements of the rod 

R. causing one or other or both of the projections e e 
to press against the end of the discs, or to be with- 
drawn therefrom, the resistance of the circuits is de- 
creased or increased in the manner described ; the 
result being that the motions of the transmitting 
rod R are repeated by the point of the pen of the 
receiver, which pen thus traces, on the paper moving 
under it, the letters formed at the transmitter 

A specimen of the writing thus received is 
given in Fig. 246. It will be seen that the words 
are not separated by an actual break in the line. 
Arrangements could be devised to effect this result 
but it is not thought of sufficient importance to 
warrant adding the necessary apparatus. 

THE ETHEKIDGE TRANSMITTER. A later form of 

transmitter, due to Mr. Etheridge, which is, in a 
measure, a return to first principles,has recently been 
introduced. It is shown separately in Fig. 247. In 
this figure, d is a plate, even with the surface of the 
enclosing box and supported by the standard h. s 
is a portion of the pen, or stylus, that is held by the 
one using the instrument in writing. It is flexibly 
attached to the rod r, the latter being supported on 
a slender, flexible rod r, shown in Fig. 248. Nor- 
mally, the upper end of the rod r. Fig. 247, is drawn 
into the notch w by a retractile spring rs. In this 
forni of transmitter the carbon discs are replaced 
by two series of resistance coils contained within 
suitable receptacles rc. The terminals of one set of 
coils are brought to upright metal strips s s s, etc., and those of the other set to s' s' 
s', etc. These sets of strips are placed at right angles to each other, as shown. The 
rod R carries a " pressure " block b, on whose sides are the set screws c, c'. On the upper 
end of each terminal strip a platinum contact point is soldered; and opposite these 
contact points, narrow, flat contact bars cb and cb' are placed , and are so arranged as 
to be easily brought into contact with the terminal contact points, ss; s's' etc, by the 
movements of the pressure block b. 

The theoretical arrangment of the coils and strips is shown in Fig. 249. 
The flexible strips cb cb' are supported at x x\ respectively. On eac con- 
tact bar a sharp projection p p' is fixed, opposite the set screw c c', on the pressure 
block. R is the top of the rod which carries the block b. The resistance coils of the 
transmitter, whose terminals are connected with the contact tongues s, s', etc., are 
^hown as at rc rc'. The coils bc, b^ c. d. etc..>^vp. «o arranged that when the contact 



FIG. 246, 




\ 



328 



AMERICAN TELEGRAPHY. 




inmm 



bar CB is jDressed by the block b against the contact tongues, the said coils are placed 
in multiple. Similarly, the coils bc', 3', c\ d\ etc., are placed in multiple when the 
contact bar cb' is pressed against them. 

This will, perhaps, be more evident by reference to Fig. 250, in which one set of 
coils is shown detached and theoretically. The coils of each series are graded from a 
higher to a lower resistance; the coils of least resistance being nearest the receiver; 
the coils of highest resistance being nearest the " ground." 
Referring again to Fig. 249. 
Normally, the end coils ec bc' and the end wires z z' are in the main circuit. 

The object of this arrangement of the coils is to 
obtain a uniform and gradual change in the strength 
of current as the coils are cut in or out of the circuit 
by the movements of the jn-essure block. 

To prevent sparking at the tongues the intermediate 
coils I, 2, 3, etc; i', 2', 3', etc., are interpolated, as 
shown. The resistance of coil i is made equal to coil 
b\ coil 2 to coil r, and so on. Likewise the resistance 
of coil i' is made equal to coil b' \ that of the coil 2' to 
coil c' etc. Thus when, for instance, the contact bar 
CB is pressed against the tongue contact s, the coil 
I is practically short-circuited by the contact bar, 
Avhile, by the same contact, as just stated, the coils ^^^ 
and b are placed in multiple. When the contact bai" 
CB is released the contact is broken at s^ and the coil 
I is again inserted in the circuit, thereby affording a path for " extra " current that 
may be set up in the coil at the moment of the break of contact. 

In practice there are 14 contact tongues and 13 pairs of coils on each series, 
and these are found to be ample to i)rovide a sufficiently gradual variation of current 
strength in the circuit for the proper operation of the receiver. There is also an extra 
coil, namely, bc or bc', termed the balancing coil, the function of which will be seen 
shortly. 

It having been found in the practice of this system that a variation of current 
strengtli from .032 to .ogo ampere gives a very satisfactory movement of the receiving 
pen, the total resistance of the transmitter coils necessary to produce that variation 
is calculated and employed. For instance, assuming the resistance of a circuit, including 
the instruments^ to be 100 ohms, and the internal resistance of a gravity battery to be 
27.5 ohms, an electro-motive force of 11.77 volts will be necessary to give the required. 

maximum current; that is, ^—'JJ- = o 90 ampere. 

100 + 27.5 
Having this maximum current on the circuit, the resistance necessary to reduce 
it to .032 ampere, is calculated. Thus, by ohms law -.VJ|=368 ohms. Then, from this 
368 ohms the resistance of the line and battery is deducted, giving 240 ohms; which 
will be the maximum resistance necessary to be introduced in the circuit by the 
transmitter. That is to say, the maximum resistance of the transmitter will be, in 
this case, 240 ohms, and it will vary from that to nothing. 

The next step is then to so arrange the resistances of the coils of the transmitter. 



ETHERIDGE TRANSMITTER. 



329 



FIG. 249. 



that they shall give a gradual rise and fall of current from the maximum to the min- 
imum, and vice versa. 

To ascertain the respective values of tlie coils for this purpose Mr. Etheridge 
prefers the following method, which will doubtless be of utility to others in arriving 
at analogous results. 

A true elliptic curve is 
constructed and its vertical 
line A, Fig. 250a, is divided 
into as many equal sections 
as there are contacts that go 
to make up the " rise and 
fall," that is, 13. The base 
line B is divided into as many 
sections as there are units 
of resistance in the transmit- 
ter, namely, in this instance, 
240. Horizontal lines are then 
drawn from each section on 
vertical a to the curve c. 
Vertical lines are then drop- 
ped from the point of inter- 
section of the horizontal lines 
with the curve, to the base 
The points at which those 
touch B will indicate the 
^ gradual resistances neces- 
sary to be secured at the ton- 
gues of the transmitter. 

For example, in a transmit- 
ter consisting of 240 ohms, 
to reduce the strength of 
current from maximum to 
minimum, the resistances 
necessary to be consecutively 
inserted in the circuit by the 
transmitter are found to be in 
ohms, o; i; 3-5; 7-5; m; 2^; 32.5; 45; 60.5; 80; 106.5; 139; 240. 

The resistances of the respective coils to produce the desired ''gradual'' resistance, is 
shown in Fig. 250. Thus the resistance of b is 240; that of c 330.25 ohms, and the joint 
resistance of b and <r is 139 olims. Again the resistance of d is 445-75 ohms and the 
joint resistance oi b c d\% 106.5 ohms, and so on to ;/, or zero. 

As, however, for the reasons given, intermediate coils are placed in, so to speak, 
double multiple with the coils b, r, d, etc., the total resistance of the transmitter at 
rest is found to be more than 240 ohms, for it will be observed, by reference to 
Fig. 249 that the coil i is placed in the circuit before the coil b. 




THEORY OF ETHERIDGE TRANSMITTER. 



^z^ 



AMERICAN TELEGRAPHY. 




To ascertain what this total resistance is the circuit of the transmitter is meas- 
ured from ^ to z; which having been done the value of a resistance such as bc, which. 
PiQ 2-0. when placed in multiple with the other coils will restore 

the resistance to 240 ohms, is calculated. In this case it 
is found to be 440 ohms, which is, consequently, the value 
of the resistance placed in the balancing coils. 

WRITING TELEGRAPH CENTRAL OFFICE. 

In Fig. 251a diagram of the central office and subscribers 
office arrangements of the writing telegraph system is 
given. 

At a subscriber's office SO, the entire equipment is in- 
cluded in one box. r is the rod of the transmitter. c 
c' may represent the coils of the transmitter, m, m' are 
the receiver magnets. A is the rod carrying the writing 
pen, the armatures of which are not shown in this 
figure, a a' are extra armatures placed below the pole- 
faces f f oi the cores of the magnets. a a' have a 
common lever l, pivoted at x. This lever has two ex- 
tensions E e'. e' extends to the "fan" or ''fly" of the clock- 
work that operates the paper-feeding mechanism. The extension e is made a part 
of one of the circuits of the system and assists in opening or closing that circuit at 
the point cp, as will be fig. 250 a. 

explained, when its arma- 
tures a a' are attracted or 
released. 

Normall}" the top of the 
transmitter rod r rests 
against two contact points 
F, p, being held there by a 
retractile spring rs. These 
contact points are respec- 
Cively connected, electrical- 
ly, to one of the main cir- 
cuits. There is another 
contact point ep, adjacent 
to R and against which it 
may be placed, ep is con- 
nected by a wire, e^ 




2^ 



/ 
I 

JS 



240 o/,ms 

with the circuit of magnet m, as indicated by the dotted line. Noi-mally that wire is 
open at ep. 

In the central office CO, n', n are annunciators, w w' are wedges capable of being 
inserted in the receptacles, or spring- jacks j j. The metallic tube w of the wedge is 
insulated from the rod w' as indicated in the figure. When thus inserted the me- 
tallic surface w makes contact with the metallic sleeve/; the rod w' making con- 



WRITING TELEGRAPH CENTRAL OFFICE. 



331 



tact with the horizontal jack. This arrangement, it will be seen, is the eqiiivalent of 
the split plugs and tubular plugs shown in " loop switch " diagrams, elsewhere. The 
annunciators are connected by wire to the sleeve y; the metal pin 2e^' with the hori- 
zontal jack. The wedges w, w are connected with batteries b, b' in the manner shown. 
Each subscriber's circuit, which is a duplicate of that shown at SO, is similarly 
connected with a spring-jack j in the central office and, at rest, the apparatus and con- 
nections at the subscriber's office and the central office are as outlined in the tiffure. 




At such times it will be seen that the circuit of magnet m, SO, is< open at ep and 
cp and the transmitter coils c, c' are short-circuited by tlie wires via the contacts p p' 
and the transmitter rod, which is connected directly to " ground. " 

When a subscriber desires to communicate with another subscriber on the same 
system he takes the handle of the transmitter and places it, for a moment, in the 
notch EP to the right. (Shown more clearly in Fig. 247.) 

This completes a circuit from the ground at SO to the ground at CO, via the an- 
nunciator N and the small battery nb. This attracts the annunciator armature, re- 
leasing its shutter, and ringing a call bell. 

The central office is, of course, equipped with a transmitter and receiver which 
he uses to ascertain the wishes of the subscriber. Having learned them, he inserts 
the wedges w w in the receptacles j j connected with the desired subscriber's office (as, 



332 



AMERICAN TELEGRAPHY, 



for instance, 2iid SO in the fignre), thereby campleting the circuit of m' via the pins 
w' and battery b' and jacks m, whereby the armature a and the lever L are attracted. 
This act closes the circuit of magnet m at cp and also withdraws the extension e' 
from the path of the fly F, thus permitting the paper to run. A bell is also pro- 
vided at the subscriber's office which can be actuated from the central office. 

THE TELAUTOGRAPH. 

This writing telegraph depends for its operation upon the resultant of two 
motions, like the original Cowper writing telegraph. The system has of late been 
much simplified and improved, now receiving its message on a sheet or roll of paper 
about 5 inches wide. It is in practical use by the United States army, etc. 

Two wires are employed between the transmitting and receiving stations. The 
mechanism of the transmitter and receiver is outlined in Figs. 252, 25 2«. p is 
the pencil of transmitter, to the point of which are connected two light rods 1 1 



Fig 




Fig. 252^. 



^j 


c 


\ 


If 




i 



£•-. 



P' 



which are connected pivotally to one end of crank levers bb, at the other end of each 
of which is attached a metal roller r r, which runs over the terminal of resistances, 
virtually similar to those shown in Fig. 249, with the similar result that the current 
is varied in each circuit as the pen is moved by the writer. {^See page 327.) 

The pen p' of receiver. Fig. 252^15, is attached to the arms r r' of the crank levers 
as shown. These latter are in frictional contact with vertical supports c c oi coils 
c c', which coils are suspended in a strong, uniform magnetic field. The coils form 
a part of the line circuits, and thus vary their positions in the magnetic field as the 
currents in the respective circuits var}^ being drawn downward as the current 
increases, and upward by the retractile springs s s' as the current weakens, with the 
result that a compound motion of the pen corresponding to that of the transmitting 
pencil is brought about. The receiving pen is automatically lifted at the receiving 
end by the following devices. An induction coil at the transmitting end which has 
two secondary coils, one connected with each circuit, is caused, to transmit pulsatory 
currents superposed upon the regular currents. The ordinary pressure of the pen in 
writing on the tablet opens a shunt circuit, which act increases the strength of the 
pulsatory currents on the line. These stronger currents in turn operate a relay, the 
lever of which closes a local circuit and thereby operates a pen-lifting magnet, where- 
upon the pen rests on the paper roll. AVhen the pressure of the transmitting pencil 
is removed the said shunt circuit is closed, the strength of the pulsatory currents is 
decreased, the action of the vibrating relay is reversed and the pen-lifting magnet 
lifts the pen from the paper. These pulsatory currents also decrease the friction of 
the receiving pen on the paper by keeping the pen in slight continual vibration. The 
paper at the transmitter is advanced mechanically as desired by the motion of a 
*' master" switch. This same motion of the switch sends a current over one of the 
wires which operates a magnetic device that advances the paper roll at tlie receiver a 
corresponding distance. Stations are called by pressing a button, virtually as in the 
case of the Etheridge system. This system requires but little attention other than 
to keep the ink fountain filled and the pen points clean. 



CHAPTER XX. 

WIRELESS TELEGEAPHY. 

PHELPS, EDISOi^, PREECE, MARCONI, DE FOREST SYSTEMS, ETC. 

The term wireless telegraphy as now generally used refers to the recently 
devised electrical methods like Marconi's and others, in which the wire between the 
transmitting and receiving stations is dispensed with, and in which electric or ether 
waves in free space are utilized. These, however, are not the only electric wireless 
telegraph systems in which the connecting wires are dispensed with, for during the 
past fifteen or eighteen years there have been in limited use a number of electric wire- 
less telegraph systems, which have sometimes, perhaps for waut of a more apt name, 
been termed induction telegraph systems, and in which electromagnetic and electro- 
static impulses of low potential and low frequency, as distinguished from electric 
weaves of high potential and high frequency, are employed. It may be noted, how- 
ever, that some of the later wireless telegraph systems have also availed of compara- 
tively low tension and low frequency waves. 

Electromagnetic and electrostatic induction wireless telegraph systems are based 
upon the phenomena of induction between wires {see page loo and Fig. 82). Such 
systems were probably first employed practically as a means of communicating to 
and from moving trains. There are at least two fairly successful systems in which 
*' induction^' is thus utilized. 



PHELPS AND EDISON INDUCTION SYSTEMS. 

The first method employed on railways in this country was an electromagnetic 
induction system, the Phelps, in which an insulated wire c, Fig. 253, is coiled in 
numerous convolutions longitudinally around a car. In series with coil c is the 
secondary wire c' of an induction coil i, also a telephone receiver t. b is the buzzer 



,. 


F 


IG. 253. 




v.... 




V '■; 


^ ' ^ i '-^ • i ^• 


_. 


'^ti] 




-•;"^ 


\ i 


^-=r^ 




1 . ; 
r" ; 


;^ 


^ 


.J> 


i; j 




1 


Q ■. 


- 1 ^ 





jr^ 



n: 



or vibrator of the induction coil, with the usual battery h. An insulated conductor 
AV is placed between the rails of the track and is led into the stations as desired. 
This conductor is grounded at both terminals. An induction coil and transmitting 
and receiving arrangements are also placed in each fixed station in series with the track 
coil. When it is desired to establish communication from, for instance, a train to a 

333 



334 



AMERICAN TELEGRAPHY. 



Station, the "buzzer" in the train, is set in motion. This originates pulsatory 
currents which flow in the coil surrounding the car, and these pulsations are, by in- 
duction, transmitted through the air to the wire w between the rails. These pulsations 
are heard in the telephone at the station as a prolonged " buzz " when the key or trans- 
mitter K is closed, but, when that key is opened, the buzz ceases, as, at such times, the 
secondary coil is open. Thus, by opening and closing the key k, long and short noises 
corresponding to the dot and dash of the Morse alphabet, may be transmitted by the 
operator in the car and received by the operator in the station. In like manner the 
" buzzer" in the station may be set in operation, and the pulsations, in traversing the 

FIG. 254. 



w 



IV 



xiii 




e^ 




^^ 


_j — -_-__^^ 


X^ 


f- Yir 


1: i 

ii 1 


i 1 


-'^ \ j 






n 


iSST 




conductor between the rails, will induce pulsatory currents in the coil around the car, 
which may be broken into acts and dashes by the transmitting operator at the station^ 
and received by the attendant in the car. 

The contacts on the transmitter k are so arranged that, when the key is closed, the 
telephone is cut out of, and the secondary coil is cut into the circuit; while, when the 
transmitter is open the reverse is the case. 

Another method of communicating to and from a moving train, and a more suc- 
cessful one from a commercial stand point, is shown in Fig. 254. 

The apparatus for setting up and receiving the '• induction " currents is practically 
the same as in the metliod just described; but the huge induction coil around the car 
and the special conductor between the rails are dispensed with. In their places the 
metallic roofing c, of the car or cars, (Fig. 254,) of the train is used as one large 
plate of a condenser; the telegraph wires w w av, by the side of the railroad track, as 
the other plate; the insulating medium, or dielectric between the plates, being the inter- 
ver ug air. 



TELEGRAPHING FROM MOVING TRAIN. 



335 



X represents the apparatus and connections of the station. Y repre- 
sents the apparatus, etc., in the car. 

The metallic roofing c of the cars is connected as shown, via the key, or transmit- 
ter K, to the earth e, through the wheels of the car. At the permanent, or stationary 
office, X, several ordinary condensers, c'c'c', are connected to adjacent telegraph wires 
w'w'w', along the route of the car. One terminal of the condensers c'c'c' at X is 
grounded, via key k, at e; the metallic roof of the car c at Y is grounded via k and 
^he wheel wx of the car — thus completing the " induction " circuit. 

The consequence of this arrangement is that when the buzzer at either station is 
operated, the condensers in the one case, and the roofs and adjacent wires in the other, 
are alternately charged and discharged ; the currents thus produced setting up in the 
telephone at the receiving office, whether in the car or station, a buzz similar to that 
referred to as established by the operation of the buzzer in the '' coil and conductor " 
method. 

The keys k k are availed of to place the telephone and the secondary coil alter- 
nately in the circuit, as previously explained. By means of this arrangement of key k 
the transmitting operator is not annoyed by the loud buzzing which would be set up in 
his telephone by the home induction coil, while, at the same time, he has an opportu- 
nity, at each opening of his key, to hear the '* breaks " of the distant station, should 
any be made. In some cases a special wire on a pole line has been erected in closer 
proximity to the track than the ordinary pole line. 

Both of these methods, the former of which is known as the " Phelps," and the 
latter as the "Edison," have been in actual operation on railroads in the country. 

THE PREECE ELECTROMAGI^ETIC METHOD. 

By an analogous method to that of the Phelps induction system, namely, the elec- 
tromagnetic method, Sir W. H. Preece in 1892 succeeded in signaling to a distance 
of over three miles without intervening wires, between Penarth on the mainland and 
the island of Flat Holm in the Bristol Channel. Two parallel wires on poles were used, 
one on the mainland, the other on the island. The wires were from one to three miles 
in length. These wires served alternately as the primary or secondary wires, depend- 
ing on which was employed as the transmitting or receiving wire. The respective 
wires were grounded at each end. Telephones were used as the receivers, as in 
■jhe Phelps system. Instead of an induction coil to set up the electromagnetic 

impulses, Mr. Preece employed a mo- 
tor-driven make-and-break wheel B, 
Fig. 2 54«, by which means a sharper 
rise and fall of current is obtained, 
which in turn has a more pronouncev.1 
effect upon the receiving instrument t. 
n"^ u— ^ ^ jg j^ii adjustable resistance. The 

•^ '^ break-wheel is shunted by a condenser c. 

Battery b consists of about 100 dry cells. 
About 600 alternations per second were used. Mr. Preece states that the 100 cells 



Fig. 254^!. 




zm£7 



S=i=^ 



iiajj fT7 



335^ 



AMERICAN TELEGRAPHY. 



with this break- wheel give as good results at 3.3 miles as a 2^ horse-power trans- 
formed into alternating currents by a transformer, owing to the smoother sinusoidal 
waves of the latter. \\"hen key K is closed, the pulsations from b are transmitted to 
the line; when open, the telephone T is in circuit for receiving signals from tlie 
distant station. "Calls "are received in this system by means of a very sensitive 
relay operated by a special transmitting device, the relay when operated ringing 
an alarm bell. 

More recently Preece has succeeded in establishing a wireless telephone circuit, 
by means of which speech is transmitted between the Skerries lightship and tiie 
mainland of Anglesey, a distance of nearly three miles, tlie parallel wire on the 
Skerries Islands being 750 yards in length, and that on the mainland 3.5 miles in 
length, the ends of each wire terminating in the sea. On these systems both mag- 
netic induction and electric conduction through the earth and water are utilized. 
The ordinary telephone transmitter and receiver are employed. It was suggested 
the vessels could hold speech with one another by this arrangement a considerable 
distance apart by having a copper wire carried from bow to stern and passing over 
the topmasts the ends of the wire being in the sea. 

HERTZIAK WAVES. 

Eemarkable as these results are, however, they have been almost totally over- 
shadowed by those wireless telegraph systems in which electric waves, or ether waves, 
are utilized, and several of which will presently be described. 

When, in 1864, Clerk-Maxwell, who was, perhaps, the most noted mathemati- 
cian of his day, made announcement of his celebrated electromagnetic theory of 
light, which theory involved the existence of electric waves in free space, many of 
the prominent physicists of the time set themselves the task of demonstrating by 
experiment the truth of this theory. It was not, however, until 1887 that the 
actual existence of electric waves in free space was demonstrated, the great honor of 
this accomplishment falling to Prof. H. Hertz, after whom such electric waves are 
now almost generally termed "Hertzian " waves. The old popidar idea of electricity 
hardly conceived it as existing outside of a wire or other metallic conductor. The 
air was an insulator, and how, therefore, could electricity exist apart from a wire! 
Maxwell overturned this view, and told us that just as under the undulatory theory 
of light that which we call light is a result of ether vibration, so also is electricity a 
result of ether vibration, and that, in so far as light and electricity differ, it is only 
a question of the rate of vibration of the ether, those undulations of the ether which 
the eye recognizes as light occurring at a rate varying from 400,000,000,000,000 to 
700,000,000,000,000 per second, while the frequency of the electric undulations of 
the ether vary from a few hundreds or thousands to over 200,000,000 per second. 

According to the undulatory theory of light, the undulations of the ether, of 
the frequency just mentioned, are set up by any source of light. Similarly, accord- 
ing to Maxwell's theory, undulations are set up in the ether by any source of electric 
oscillations, analogously, for example, as waves are set up in the atmosj^there by a 
source of sound. Also, as those ether waves which correspond in frequency to light 
atfect an organ of sight when they fall upon it, and as sound waves aHect an organ 
of hearing when they fall upon it, so, it was reasoned, should the electric waves of 
the ether aifect a suitable electric " eye," or receiver, when they fall upon it. 

The manner in which Prof. Hertz proceeded to show the existence of electric 
waves in free space was, briefly, as follows : It was already known that electric 
oscillations could be set up in a well-insulated wire or conductor; in fact, that the 
discharge of the Leyden jar is made up of a series of electric oscillations, as had been 
shown by Lord Kelvin in 1853. Hertz set up electric oscillations by .neans of an 



HERTZIAN WAVES. 



335^ 



Fig. 254(5. 




electric oscillator, shown in Fig. 254J. This consists of an ordinary large induction 
coil, I, the terminals of the secondary coil being connected to brass balls, or 
knobs, 1 1, and to Avhich short metal rods, or cylinders, w, are attached. The knobs 
are separated by a small air space or spark gap s, across which 
sparks jump when the coil is in operation. At snch times elec- 
tric oscillations are set np, the rate of which varies with the 
inductance, capacity, and resistance of the circuit, according 
to the formula, t = 27r 4/kl, where T is the time in seconds, 
n (Greek letter^^i") is the ratio of circumference to diameter, k is 
capacity, and l the inductance of circuit, or T = 6.2832 t kl. 
It is assumed that inductance is the equivalent of inertia in 
mechanics, while capacity is the equivalent of elasticity. A 
charged condenser or other conductor possesses potential en- 
ergy. In the act of discharging, the potential energy of the 
condenser decreases, while kinetic energy (momentum), due to 
the current accompanying discharge, will be acquired. Hence, 
when potential energy has fallen to zero (and assuming little 
resistance in the circuit) the current will still flow. This 
current charges the condenser oppositely and it again possesses 
potential energy, whicli, when the charging current ceases, will 
again set up kinetic energy, and thus electric oscillations are established and con- 
tinue until dissipated by the resistance of the circuit, etc. The resistance of such 
circuits being comparatively small is neglected in the above formula. Certain Hertz 
< scillators are found by calculation to oscillate at the rate of ten millions per second ; 
others at the rate of 300 millions, etc., varying with size cf balls. 

Hertz assumed that if the electric oscillations thus produced set up corresponding 
waves in the ether of free space, these waves should, in turn, set up electric oscilla- 
tions of corresponding frequency in a suitable receiver, or " eye," within the range of 
their influence. He, therefore, adopted as a receiver of these waves, a circular 
<'opper wire, c/. Fig. 254^, about 16 inches in diameter, but broken at one point. 
On the ends of this wire he placed small metal knobs, the distance between whicli 
could be easily regulated by a micrometer screw. This wire was held by an insulated 
handle, a few feet from the oscillator. With the room darkened, minute sparks 
were observed passing between the discharge knobs of the receiver; and the results 
of this simple experiment have been generally accepted as proof of the existence of 
electric waves in free space. Hertz, however, was not satisfied with this demonstra- 
tion of the accuracy of Maxwell's theory, but also, in the course of his subsequent 
masterly experiments, shov/ed tluit, like sound, heat, and light waves, the Hertzian 
waves could also be reflected, refracted, concentrated in parallel rays, etc. 

By the Hertz receiver the distance at which electric waves could be detected 
was very limited, pci-haps ten or twelve feet at most, and hence it is not likely that 
much would have been done in the utilization of Hertzian waves for telegraphic pur- 
])oses h;;d progress rested there. Fortunately, it did not. Shortly after the experi- 
ments of Hertz, Dr. Branly discovered that loose metal filings, which in a normal 
state have a very high electrical resistance, lose this resistance in the presence of 
electric oscillations and become practically conductors of electricity. This he showed 
by placing metal filings in a glass tube, h, and making them part of an ordinary 
electric circuit. Fig. 2546'. When electric waves are set up in the neighborhood of 
this circuit, electromotive forces are generated in it which appear to bring the filings 
more closely together, that is, to cohere, and thus their electrical resistance decreases, 
from which cause this piece of apparatus — the tube and its filings — is termed a 
"coherer." Hence, the receiving instrument, G, in the figure, which may be a 
galvanometer or a telegraph relay, that normally would not" manifest any sign of 



335^- 



AMERICAN TELEGRAPHY 





r 


— t^^^:?^»^>;'^i:^fj>kki----| — 




' 


Ls 




c» 




1 


1 


I G ^ 




1 


3 L 



current from the small battery, B, will be operated when electric oscillations are set 
up. Prof. Branly further found that Avhen the filings had once cohered they retained 

their low electrical resistance until shaken apart, 
Fig. 254^. f^^ instance, by tapping on the tube. 

In 1894 Dr. O. J. Lodge showed that the 
Branly coherer could be employed to transmit 
telegraphic signals, and in order that the filings 
might not remain "cohered" after the cessation 
of the electric oscillations, he devised a mechan- 
ical "tapper," on the principle of the common 
electric door-bell, the hammer of which was 
caused to tap the glass tube as long as the elec- 
tric oscillations continued. The filings thus virtually take the place of a key in 
the ordinary telegraph circuit. In the normal state the key is open; in the presence 
of electric oscillations the key is closed. Thus, by opening and closing the key for 
a longer oi- shorter period, signals corresponding to dots and dashes may be pro- 
duced. In other words, by setting up electric oscillations for periods of time corre- 
sponding to dots and dashes, messages may be transmitted, and if at the receiving 
station a recording instrument (controlled by the coherer), such as is used, for 
instance, in the Wheatstone automatic telegraph system, be provided, a record of 
the message in dots and dashes is obtained. 

In 1 895-1 896 Poppolf and others utilized the coherer to show the existence of 
atmospheric electricity, using for the pur^^ose a vertical or aerial wire connected to 
the coherer, as shown in subsequent figures. 



MARCOXI WIRELESS TELEGRAPH. 



In wireless telegraphy as at first operated by Marconi there were employed an 
electric oscillator 0, Fig. 254^/, with the primary and secondary coils ^ and s of an 
induction coil i, the discharge balls h h, and an aerial wire A, connected to the 
secondary coil and to earth by wires tu w' as shown, forming the transmitter circuit. 
The receiving circuit comprised a filings coherer k, Fig. 254^, a tapper t in a local 
circuit ^', and vertical wire a. It Avas by modifying, improving, and perfecting these 
devices, and by adding others, that Marconi has been enabled to obtain prac- 
tical results. The improvements and additions that perhaps conduced more than 
anything else to the first successful results obtained by Marconi were those that 
related to the coherer and the vertical wire. The sensitiveness of the coherer he 
increased greatly by diminishing its size, as indicated in Fig. 254^, compared with 
the Branly coherer, and by employing a mixture of nickel filings and sdver — 90 per 
cent, of the former and 10 per cent, of the latter metal. He also placed the few 
filings used in a vacuum. The other instruments shown in Fig. 254^ are the relay, R, 
controlled by the coherer, and an ink-recording instrument, E, controlled by the 
relay. This figure illustrates the earlier arrangement of Marconi's devices. In it 
the coherer is directly connected with the lower end of tlie vertical wire by one of 
its terminals, and with the earth by its other terminal. The operation of tlie trans- 
mitting and receiving apparatus is practically as follows : The closing of key K of 
the primary circuit 2^ of the induction coil sets up current of high potential in 
secondary circuit s .<?. When the potential is sufficiently high, sparks jump across 
the air gap between l h and electric oscillations are set up in A and iv iu\ and ether 
waves are emitted in space. By opening and closing key k to form dots and dashes, 
the sparks are correspondingly broken into short and long periods. Normally the 
lever V of tapper t is given a tension which holds it against the contact c. The 
armature-lever I of relay r is also normally on its back stop x. Hence at this time 



MARCONI WIRELESS TELEGRAPH, 



335^ 



local circuit of battery 1)' is open. When the filings cohere on the arrival of the 
emitted waves, relav a is magnetized by one dry cell b and its lever I moves over to 
contact x', closing circuit of battery 1)\ and the electromagnet of x attracts its ai-ma- 

FlG. 



t 



w: 






Fig. 254^. 

h b 



254^, 



w* 







^^1 










ture, which opens the circuit of h' at c. At once the armature of t flies back on its 
contact point, at the same time striking the tube, decohering the tilings, and opening 
the local circuit of R at x'. Immediately, however, the filings again cohere, assuming 
the oscillations to continue, with the result that R is energized, again closing cii- 
cuit of b' at x\ whereby T is again magnetized, and the actions just described are 
repeated many times in a second. In addition to the apparatus outlined in 
Figs. 254^/, 2546, a number of impedance or choke coils such as ck, and non-induc- 
tive coils essential to the practical operation of the system are employed. The choke 
coils are furnished with fine iron wire cores to increase the magnetic effect; the non- 
inductive coils are wound back upon themselves like rheostats, and are thus non- 
magnetic. In practice it is found necessary to enclose the coherer, the tapper, 
transformer coils ( /, Fig. 254?') and the wires connected therewith in a box sheathed 
with iron. This sheathing is connected to the earth. R is usually a sensitive polar- 
ized relay of from 1200 to 10,000 ohms resistance. It is operated witli one cell b. 
•One reason for the use of a sensitive relay is that with more than one cell the coherer 
may act continuously. It is necessary that no sparks shall be developed at any of 
the contact points of R or tapper T. To prevent such sparks these contacts are 
shunted by non-inductive resistances of from 1000 to 4000 ohms, and in some 
instances with a condenser. The Morse register E is placed outside of the box, the 
wires leading out to it passing through a choke coil at the box to prevent external 
oscillations following the wire. A call bell is operated by the lever of the register e. 

Beginning his experiments in Italy in 1895 with vertical wires twenty feet in 
height, Marconi found that he could get signals at a distance of one mile, and that 
by doubling the height of the vertical wire at both stations signals could be trans- 
mitted to four times that distance. Thus, with wires forty feet high, he could signal 
four miles, and with Avires eighty feet high, sixteen miles. Since then Marconi has 
steadily increased the height and number of aerial wires until in his latest work 
these wires, over 250 feet in height, are numbered by the score, and the distance to 
which signals are transmitted through free space is over 2500 miles, as will be 
described in more detail subsequently. 

To transmit and receive signals a distance of say 186 miles, with the apparatus 
outlined in Figs. 254^!^, 254^, about 150 watts (10 volts and 15 amperes) are necessary, 



335^ 



AMERICAN TELEGRAPHY. 



Fig. 254/. 



or nearly one fifth of a mechanical horse-power. The source of the electrical energy is 
a storage battery, which latter is sometimes charged by a number of dry cells in mul- 
tiple. In passing, it may be remarked that an ordinary telegraph relay may be 
operated at a distance of 186 miles at an expenditure of three watts at the trans- 
mitting end of a telegraph wire, or with one fiftieth of the energy used in operating 
the electric oscillator in question. The actual energy required to operate the tele- 
graph relay is about 0.24 of a watt, the rest of the energy being consumed in the 
wire itself. It must not, however, be assumed from this that the coherer is a less 
sensitive electric receiver than the relay; nor will it be, when it is reflected that the 
electrical energy expended in the case of the relay is, so to speak, mainly confined to 
the wire, as, analogously, sound waves are confined within a speaking-tube, whereas 
the electrical energy of the oscillator is radiated into space in every direction, and 
thus but a small portion of the total energy reaches the receiving vertical wire. It 
has been calculated that the electrical energy received on a surface one foot square 
at a distance of but one mile from the oscillator is less than one-three-hundred-mil- 
lionth of the total energy radiated, and it may be noted, the energy actually radiated 
as electric waves is a mere fraction of the energy consumed in and at the oscillator 

From the results obtained by Marconi and others, it appears that the efiect of 
increasing the length of the vertical wires is to give a greater radiating surface at the 
transmitting end and to present at the receiving end a larger surface upon which a 
greater number of circles of waves may fall, each circle of waves adding to the electri- 
cal energy set up in the receiving vertical wire. 

The vertical wire or wires for ships and for short distances is usually of stranded 
copper, about ^ inch in diameter, although Marconi for this purpose has used also 

strips of Avire netting, about 2 feet broad. The 
wire or netting is supported by masts of proper 
height, securely guyed. It is not necessary 
that the wire be suspended strictly vertically 
so long as the desired vertical height is obtained. 
The wire is thoroughly insulated from the mast 
or tower at the top by sticks of rubber or 
ebonite, and is led in through an open window 
or hatchway to the room where the transmit- 
ting and receiving apparatus are situated. 
Although the discharge knobs are separated 
by an air space of only about half an inch, the 
induction coil used in connection with the 
oscillator is often capable of producing a spark 
that wall jump ten or twelve inches through 
air. The actual appearance of the induction 
coil, discharge knobs, vertical wire, etc., is 
illustrated in Fig. 254/', which represents a 
military signaling outfit. The heavy current 
and high pressures in the circuits of the oscil- 
lator have led to the adoption of a much larger 
key for manipulating the oscillator than is 
used in ordinary Morse telegraphy. 
The specimen of a dot and dash wireless telegraph record given in Fig. 254^ is 
a facsimile of bulletins "caught on the wing" during the yacht races of 1899 in 
New York Harbor. Jilr. Marconi had his apparatus on the steamship Ponce^ and 
■was sending bulletins of the progress of the race to the Mackey-Bennett cable ship, 
some miles away, when this specimen and many others were recorded by a set of 
Clarke wireless telegraph apparatus which the writer was supervising on the steam- 




SYNTONIC WIRELESS TELEGRAPHY. 



335/ 



ship La Grande Duchesse. This was probably the first instance of tapping Hertzian 
wave signals, in the United States at least. It will be understood that Shr. is an 
abbreviation of Shamrock. Other abbreviations were used in these bulletins, as Col. 



H 



R 



D R 



Fig. 254,§-. 



W S 



W 



Y 



for ColumUa; abt. for about; bd. for board, etc. The present speed of signaling 
b}' wireless telegraphy is from ten to twenty words per minute. With the filings 
coherer as a detector of the receiver oscillations, but with the later type of detectors, 
known as anti-coherers, auto-coherers, etc., and by the use of the telephone as a 
receiver, a speed of 30 to 40 words per minute is attained. Instances of such de- 
tectors are those used by Marconi and De Forest, which will be described herein. 



STNTOKIC WIRELESS TELEGRAPHT. 

At an early period of the practical history of Hertzian wave telegraphy it was 
seen that the usefulness of this art might be considerably curtailed by the fact that 
but one message could be transmitted between any two stations within the sphere or 
*' radius" of influence oi: a transmitter, since the attempt to transmit even two mes- 
sages at one time would result in an unintelligible mixture of both messages. Several 
inventors have been more recently at work trying to overcome this defect, and, it is 
claimed, with success, notably Dr. Lodge, Sig. Marconi, and Dr. Slaby. The plan 
followed by these gentlemen has been that of employing a syntonic or tuning 
method; that is, the transmitting and receiving circuits are adjusted or '^ attuned'^ 
to a given rate of electrical oscillations. 

It is a well-known experiment that when two tuning-forks, having an identical 
fundamental rate of vibrations, are placed in suitable proximity, either fork may be 
set into vibration by air waves set up by the other fork, and neither will be set into 
vibration by another fork of a different note. The tuning-fork is a persistent vibra- 
tor by virtue of t\Vo qualities which it possesses, elasticity and inertia. When struck 
a smart blow, it moves from its point of rest; directly its elasticity returns it to its 
point of rest, its inertia carries it past that point, its elasticity returns it to zero 
point, inertia carries it past, and so on, until the resistance of the air and other 
causes stop it. Analogously, an electrical circuit may be given, in almost any de- 
sired proportion, the equivalents of mechanical inertia, elasticity and resistance, in 
inductance, capacity, and ohmic resistance, respectively; and the rate of electric 
oscillation of a circuit may be varied by varying these factors — the smaller the fac- 
tors, the higher the rate of oscillation. {See page 335^.) 

W^hen, then, the receiving circuit of a wireless telegraph system is accurately 
tuned to oscillate in harmony with the transmitting circuit, by giving the respective 
circuits practically equal inductance, capacity, and resistance, the receiving circuit 
will respond only to the oscillations set up by a transmitter correspondingly tuned. 
In experimenting, Marconi and others have, it is stated, found that perfect syntony 
between the respective stations is not absolutely essential, but that if there is a 
marked divergence of frequency of oscillation between them, the receivers will 
not respond to any but their correspondingly attuned transmitters. 

The arrangement of Marconi's tuned transmitting and receiving circuits is out- 
lined in Figs. 254//, 254/. It will there be seen that the oscillator and the coherer 
k are not connected to the earth, as in Figs. 254^/, 254^', but that a small induction 
coil or transformer, t, is interposed. In Fig. 254/*!, A is the vertical wire which is 



OOD<b 



S£- 



AMERICAN TELEGRAPHY. 



attached at its lower end to a coil of wire w. The end of the wire s, which forms 
part of the secondary wire of the induction coil t, may be connected to any desired 
turn of the coil w. By this means the inductance of the vertical wire circuft may be 



Fig. 254//, 



Fig. 2542. 





varied, and its oscillation period thereby be made to correspond with that of the cir- 
cuit o, of the oscillator, which includes the primary wire ;j of t; c is an adjustable 
condenser of very small capacity, by varying which the oscillation period of the circuit 
may readily be varied. Leyden jars are frequently used for tliis service. A key k 
controls the primary circuit, as snown, and thereby, the oscillator circuit; I is the 
induction con of tlie oscillator. 

The tuned receiving apparatus is shown in Fig. 254/. In this figure, a is again 
the vertical wire with the turns of wire, w, to Avhich is attached the j^rimary wi;e p 
of the induction coil t; .v .s is the secondary of the same induction coil; /lis the 
coherer, and c is a condenser. The induction coil T acts virtually as a step-up 
transformer, which, it is claimed, materially enhances the electromotive forces of the 
received oscillations, and thus increases the signaling distance. In this case the 
condenser consists of a few sheets of tin foil or copper, the alternate sheets beiug 
separated from each other by thin sheets of paraffin paper. 

Marconi has found it important that the oscillation period of the coherer circuit 
shall be the same as, or an octave of, the oscillation period of the vertical wire cir- 
cuit. This can be done by making the secondary coil s s of the coil T equal the 
length of the vertical wire a. The transmitter circuit is then adjusted so that its 
oscillation period corresponds with that of the receiving circuit. This is brought 
about by varying the capacity of the condenser in Fig. 254/^ The method of obtain- 
ing this " balance," as practised by Marconi, is to begin with very little capacity in 
the condenser, and adding to it until the best results are obtained at the receiving 
station. If, when the best results are obtained, still greater capacity is given to the 
condenser in the transmitting circuit, the signals fade away, showing that then the 
two circuits are out of harmony. 

Marconi also found that by means of tuned apparatus a much greater distance 
may be reached, with a given source of electrical energy and height of wires. For 
example, a transmitter which would affect a tuned receiver thirty miles away would 
not affect a non-tuned receiver 160 feet distant. This, it may be assumed, is because 
in the case of the tuned receiver the faintest oscillations, or electromotive forces, set 
up in the receiving circuit by the incoming waves, are in unison with those waves, 
and successive incoming waves amplify the oscillations in the receiver circuit until 
they affect the coherer (in other words, resonance comes into play) ; Avhereas the 
oscillations which the same waves tend to set up in the non- tuned receiver circuit 
are, so to speak, out of step with the natural rate of oscillation of the non-tuned 
circuit, and thus as frequently oppose as assist the natural oscillations of the circuit. 

In connection with the experiments carried on by Marconi, it is reported that 
two different messages have been received at one time on a vertical wire, two sets of 



WIRELESS TELEGRAPHY. 



335^^ 



receiving apparatus, each attuned to a different rate of oscillation, being connected 
with the same wire. To those who have Jiad experience with Gray's harmonic sys- 
tem of wire telegraphy, in which three and four instruments, attuned to transmit 
and to receive different rates of electrical current pulsations, have been successfully 
and separately operated on one wire, this will not appear astonishing, since it is quite 
conceivable, if it be granted that wireless transmitting and receiving apparatus can 
be successfully attuned, that two or more receiving instruments might be connected 
with one vertical wire, and each set of apparatus select and respond only to the par- 
ticular rate of oscillations to which it is attuned. However, if by the use of tuned 
apparatus nothing else were gained than the ability, with a given amount.of electrical 
energy and a given height of vertical wire, to transmit signals to a greater distance 
than is possible with untuned apparatus, it must be considered a decided advance in 
the art, and judging by the whole progress of electrical telegraphy, it is safe to say, 
when so much has already been achieved, that the necessary improvements to obtain 
at least practical freedom from intei'ference between adjacent apparatus will ulti- 
mately follow. Tuned wireless systems are known as ''closed," untuned as " open" 
systems. The one is a persistent vibrator, the other is quickly dampened. Com- 
pare Fig. 254^/, Fig. 254/i. 

MARCONI LOXG-DISTAXCE AVIRELESS TELEGRAPH. 

From the more recent experiments it appears that, given a sufficiently powerful 
transmitter and a sufficiently sensitive receiver, there is no limit to the distance to 
which signals can be transmitted by electric waves. It was at first thought that this 
distance would be limited to within a few hundred miles by the curvature of the 
earth, it being impracticable to secure masts or other means of support for the aerial 
wires high enough to surmount the convex surface of the earth between points sev- 
eral hundred miles apart, and it being supposed that the earth would prove a barrier to 
the electric waves traveling in straight lines like light waves, which latter it is well 
known are obstructed by substances opaque to light. A number of theories have 
been advanced to explain the fact that signals are received at distances much beyond 
what would be possible did the earth intercept the waves traveling in straight lines. 
One, due to Kennelly, assumes that the atmosphere at a distance of say 50 miles 
from the earth's surface possesses an electric conductivity about 20 times greater than 
ocean water; further, that electric waves of the frequency used in wireless teleg- 
raphy, propagated through the atmosphere and the ether, are reflected by the elec- 
trically conducting surface of the ocean (the ocean as a conductor being opaque to 
electric waves of a frequency of millions per second). The conducting strata of air 
and the surface of the ocean thus give an upper and a lower conducting surface. 
The upper conducting surface may have little effect on electric Avaves that are trans- 
mitted a few miles only, but on waves that are transmitted to a distance that is 
large compared with 50 miles, the waves may find in the upper conducting strata of 
air another reflecting surface, and thus may move horizontally outwards in a 50- 
mile layer between the upper and lower reflecting surfaces, to a great distance. 
Another theory, advanced by Rankin Kennedy, is that the action upon the electric 
wave detector in long-distance wireless telegraphy is due to electric oscillations set 
up in the earth itself considered as a sphere or globe insulated in space. Xominallv, 
the globe is electrically neutral, all parts of it being at equal potentials, but when 
the electrical condition is disturbed, as by an electric oscillator, the disturbance 
spreads over the whole globe and may be detected at any other part of its surface by 
a sufficiently sensitive electric wave detector. Still another theory, due to Taylor, 
is, in brief, that the waves travel over the earth's surface or that of the ocean, as 
they Avould over the surface of a conducting plate, in all directions liorizontally from 
the vertical wire, the base of the waves following the contour of the earth or ocean, 
traveling over curved or round conducting surfaces, and being absorbed by precipi- 



335^ 



AMERICAN TELEGRAPHY, 



tons conducting surfaces, and passing through, non-conducting substances, since the 
latter are transparent to these waves. 

In the latest Marconi arrangement of the equipment for transatlantic and other 
long-distance wireless transmission, the aerial wires at the land stations are sup- 
ported on high masts or towers, preferably the latter, in order to withstand storms, 
as shown in iig. 254^. These tow^ers, of which there are four, are about 220 feet in 
height, and at South Wellsfleet, Mass., they stand on a sand cliif about a hundred 
and fifty feet above sea level. A multiplicity of vertical small copper wires are sup- 
ported by horizontal wires strung from tower to tower as shown. Ihe vertical 

wires converge as indicated and 
Fig. 254;. ^j.g thence led into the instru- 

ment room. At the same sta- 
tion there is a windmill used 
to drive a dynamo to charge a 
storage battery. A gas engine 
is employed to run the generator 
used in setting up the powerful 
oscillations necessary for trans- 
atlantic signaling by this sys- 
tem. Details are not yet ob- 
tainable in full regarding these 
stations. At the Poldhu (Corn- 
wall, England) station, it is 
understood that a 20-kilowatt 
generator developing 2000 volts 
was used. This voltage is raised 
by "step-up^' transformers (a 
type of induction coil) to per- 
haps 100,000 volts on the aerial 
wires. Owing, however, to the 
losses in transformation and at the spark gaps only a small fraction of the energy of 
the generator is radiated. It is clear that means must be provided for obviating 
danger at the opening and closing of the transmitting key, where strong currents 
and high potential are used. This is sometimes done by opening the circuit in oil, 
special keys being designed for the purpose. 

The FLEMING TRAXSMiTTiXG SYSTEM. — In Fig. 254^' is outlined a transmitting 
system designed by J. A. Fleming, for the Marconi AVireless Telegraph Comxpany, 
for long-distance signaling, the description herewith of which is condensed with slight 
changes from the British patent specifications. In the figure, d is a 20 or 25 kilo- 
watt alternator, at 2000 volts more or less, with a frequency of 50 per second, t is 
a transformer the primary wire of which is in series Avith D. This transformer raises 
the E. M. F. to about 20,000 volts, charging condensers c, which discharge across spark 
gap s, in secondary of T, and oscillations are set up in the primary of t', which oscilla- 
tions are again transformed to higher e. m. f. in t\ charging condenser c', which dis- 
charges across s', setting up oscillations in t% which still further increases the e. m. f. 
thrown wpon the aerial wire, or wires A. By means of this double or treble trans- 
formation the E. M. F. at the aerial wires is sufficient to give a s]^ark of about twelve 
inches, perhaps equal to over 100,000 volts. If oscillator circuit 0^ be omitted the 
secondary of transformer t^ is connected to the aerial wire. Condensers c are of 
special construction, consisting of a number of stoneware boxes filled with doul)le-boiled 
linseed oil, in which twenty glass plates, 15.5 inches square and coated with tin foil 
on both sides, are placed. Eighteen such boxes in parallel give a total capacity of 
about one microfarad. They are connected as shown at c, so that the length around 




WIRELESS TELEGRAPHY. 



3357 



and through any condenser and the spark gap and primary of transformer t' shall 
be equal, to the end that all condenser discharges shall travel in the same time to 
spark gap s and all have the same frequency. The capacity of condensers c' is ad- 
justed in such manner that oscillator circuit o' has an oscillation period equal to the 



9 



Fig. 254>^. 



■ 111^^* 




secondary of t'^ and the aerial wires. Analogously, the other oscillation circuit o 
and transformer circuits are suitably attuned to each other, by varying the induct- 
ance or capacity, for which provision is made in the apparatus. 

To obviate opening and closing the primary circuit of D tv/o choke coils i i' 
having movable iron cores m m\ are placed in the primary circuit of t and D. The 
iron core of iii' is so adjusted that as much current as can safely be allowed to flow 
through primary of T shall normally pass. The core w of i is let all the way down, 
and it entirely impedes the flow of current in the primary of T. Coil i can, however, 
be short-circuited by key K, at which times the current in said primary attains full 
value. Thus the circuit of D is nut opened in the usual sense. Key K is of the 
type that is opened at a number of places, ten or twelve, to render the spark harm- 
less, and the switch is opened in insulating oil. 

Marcone long-distais^ce receiver- magnetic auto-coherer. — For wire- 
less transmission in excess of a few hundred miles the filings coherer with a relay 
as receiver is not sufficiently sensitive, hence, as already intimated, recourse has 
been had to more sensitive detectors, termed auto-coherers and anti-coherers, in which 
the telephone is used as the receiver, that instrument, it is known, being responsive 
to exceedingly minute currents. In the auto-coherer no tapping back is required, 
the instrument resuming its normal electrical condition automatically directly the 
electric oscillations cease. An auto-coherer designed by Marconi, and known as the 
magnetic detector, has been used with much success in his transatlantic and other 
long-distance work. It consists of a primary and secondary coil of fine copper wire 

w w^, Fig. 254/, wound over a core c of fine iron 

Pig. 254/. wires. The inner Avire ic may be connected with 

^^ / - ^^^^ aerial wire in the manner described in the caec 

^U r\ n . f^ ■^ n^.^^ ^ A A ^Q rf^^ I ^^ ^^^^ filings coherer. The outer wire contains 

L\ \ \ \ \j> VWAA W \\ M 1 ^ ' I in its circuit a telephone receiver t, but no battery. 

A permanent magnet M is placed near an end of 
the core c. The magnet is revolved by clock-work 
at the rate of about thirty revolutions per minute. 
This detector of electric waves is based on the observed fact that when a magnet, such 
as core c, is undergoing regular slow changes of magnetism (which slow magnetiza- 
tion, by reason of hysteresis, is retarded and lags behind the magnetizing force), elec- 
tric oscillations produce rapid changes in the magnetization of the magnet, with the 



J 



?i^ 



w' 



ur 



335^ 



AMERICAN TELEGRAPHY. 



result that currents are set up in the coils surrounding the core, which are heard 
in the telephone receiver as long and short sounds Avhen signals are being received. 

With electric wave detectors of the automatic type the action seems to be practi- 
cally instantaneous, unlike the filings coherer, in which time is lost in cohering 
and in tapping back. A much higher rate of transmission with detectors ot the 
Marconi and De Forest type (to be described) is therefore possible ; li sj)eed of 
thirty-five to forty words having already been attained. It is apparent that when 
detectors of this type are employed and the current is too weak to oper.ite a relay 
there will be no automatic ink record of the received messages. Marconi, Jiowever, 
anticipates that it will be possible to find a suitable recorder in connection with the 
magnetic detector, in which event he predicts a speed of loo words per minute. For 
calling, a coherer with alarm bell is used in connection with auto-detectors other- 
wise the attendant must keep the telephone at his ear continuously. 



DE FOREST WIRELESS TELEGRAPH. 

This system, shown theoretically in Figs. 254?^,, 2^411, is used successfully ,u 
the United States. In this system the usual induction coil for setting up oscilla- 
tions is dispensed with and instead a motor generator d (see Fig. ^la) is employed, 
which receives direct current at no volts from any available source as a motor, and 
as a generator delivers an alternating current of 500 volts. Or where current is not 
available to operate an electric motor, an engine-driven generator is employed. T 
is a step-up transformer which transforms the current to 25,000 or 50,000 volts. 
This latter current charges a condenser c, or Ley den jars (a capacity equal to about 
five quart jars is used). The condenser discharges across the spark gap s, setting up 
electrical oscillations in aerial wire a. Instead of the usual balls at the discharge gap, 



Fig. 254/;/. 



Fig. 254;?. 




.-•t 



rt=l- 



ri=<i 



JVWVWA 

a brass disc between two small brass balls is employed, the latter being adjustable^ 
the disc stationary. The balls are supported in a vertical position on corrugated pillars 
of ebonite; t' is a choking or impedance transformer with a ratio of transformation 
of unity, that is, the primary and secondary have the same winding. Its function 
is to prevent the high potential curi'ents jumping through to the armature of D; K is 
a Morse transmitting key, by means of which the train of oscillations is broken into 
dots and dashes of the Morse code. The contacts of this key, which are in the cir- 
cuit of D and primary of /' /, are opened in oil to prevent harmful sparking. The con- 
tacts of this key are so arranged that the aerial wire is automatically connected with 
the transmitting circuit when the key is closed, and with the receiving circuit when 
the key is open, which practice is also common to the Marconi and other systems. A 
general resemblance of the Fleming transmitter. Fig. 254^, and Fig. 2547», may bo 
noted. By this arrangement of transmitting apparatus much greater power is ob- 
viously obtainable than by the ordinary induction coil. 

One arrangement of the De Forest receiving circuits is shown theoretically 



WIRELESS TELEGRAPHY. 335/ 

in Fig. 2^4)1. The wave detector k used in this system is termed the "responder." 
It is an auto-coherer, and also an anti-coherer in that normally its resistance is low, 
but increases when oscillating currents traverse the receiving circuit. This detector 
consists of a tube in which two metal rods are placed, practically as in the case of 
the tilings coherer. In the space between the ends of these rods a viscous liquid, such 
as glycerine, is placed, and in the liquid small pieces of metal, such as lead oxide, are 
suspended. AVhen current from cell B alone is flowing, these filings build up bridges 
which close the gap, electrically considered, but when electric oscillations are set up in 
the circuit electrolysis takes place with an explosive generation of hydrogen gas, which 
destroys the bridges, thereby largely increasing the resistance of the circuit. On 
the cessation of the oscillations the bridges at once re-form automatically under the 
influence of battery B. The variations in the strength of current thus produced 
affect the telephone t\ and a note or sound corresponding in length to the dots and 
(lashes transmitted, is set up* in that instrument. R is a resistance used to regulate 
the current in the circuit. In series with telephone t is the condenser c, ^\hicli ac- 
centuates the sound in the telephone. 

No attempt is made to utilize syntony or tuning in the De Forest system, and 
apparently it has not thus far been deemed necessary, dependence being placed upon 
the transmission of powerful waves and the highly sensitive respond er employed. 
Tests of this system have recently been made by the United States Navy Depart- 
ment, between Washington, J). C, and Annapolis, Md. At each station masts 180 
feet high are used. From these masts five wires 200 feet in length are fanned out, and 
joined at the bottom. The "ground'' consists of two copper plates, two by six feet 
each, buried six feet in the earth. It is understood that this company will shortly 
have constructed a 175 foot tower at Cape Ilatteras, for communicating with passing 
ships and also with Block Island off Rhode Island, 300 miles distant, where a similar 
tower is being constructed. The power at these stations will be four kilowatts. For 
shorter distances, machines generating about one kiloAvatt are sufficient. Long dis- 
tance signaling across the Pacific is also said to be contemplated by this system, with 
stations having a capacity of forty-five kilowatts. 

The De Forest system has been utilized as a means of transmitting stock news 
from the street to brokers' offices in New York City. The street equipment is carried 
in an electric automobile, a rod from th^ vehicle supporting a comparatively short 
vertical Avire. For this work an induction coil is used in setting up the electric 
oscillations, current being supplied by the storage battery of the automobile. The 
13ranly-Kopp Company of France has a somewhat similar method of distributing 
news in operation in Paris. It may be noted that balloons and kites have been 
repeatedly used for upholding the vertical wire when masts have not been available. 



Numerous other wireless telegraph systems have been invented within the past 
few years, among others the Braun or Siemens-IIalske, the Slaby-Arco, the Fessen- 
den, the Lodge, and the John Stone Stone. Of these, at least the Braun and the Slaby- 
Arco are in operation in Europe. It is, however, not within the present scope of 
this chapter to describe these various systems. From the fact that suits and counter- 
suits at law between a number of the prominent wireless telegraph interests are pro- 
ceeding, for infringement, it may be assumed that there is a tendency towards the 
employment of more or less similar methods and apparatus. For a more complete 
treatment of the entire subject, as well as a detailed description of the systems men- 
tioned and others, the reader maybe referred to the author's work on ''Wireless 
Telegraphy, " for synopsis of contents of which see last pages. 



CHAPTER XXI. 
SYNCHRONOUS MULTIPLEX TELEGRAPHY. 

In ordinary manual telegraphy tlie speed of transmission of the average operate* 
is from 25 to 40 words per minute. Assuming that there are 25 pulsations to the 
average word, we get a total of, say, 600 electrical pulsations as the maximum num- 
ber of dots which an operator is capable of making, per minute. It is known that 
500 or more pulsations, per second, can be successfully transmitted on moderately 
long overhead circuits. 

From the knowledge of these and other facts, the idea was conceived that, if 
means were provided whereby a telegraph wire could be distributed among four, six 
or more operators, giving each of them exclusive, momentary, use of the wire, in ro- 
tation, so rapidly that it would not be possible for any one of them to make a dot 
before the wire would be assigned to him, the same wire could be utilized to transmit 
4, 6, or more messages at, practically, the same time on one wire. 

In order that this might be done satisfactorily it was evident that the correspond- 
ing transmitting and receiving instruments at the near and distant stations should be 
placed in connection with the line wire at identical instants of time. This en- 
tailed devices for securing a certain synchronous action of the apparatus so that the 
aforesaid requirement could be met, and, hence, the title of this system of telegraphy. 

The apparatus for securing this result consists of a revolving wheel, due to Paul 
La Cour, at each end of a telegraph line, the wheels revolving, as nearly as possible, 
at a i^recisely uniform rate of speed, and electrical and mechanical devices for the 
maintenance of this uniform rate of rotation. 

The motive power of each wheel is an electric-motor, or, it may be said, the 
wheel is part of an electric-motor. 

The motor is operated by electrical pulsations caused by a tuning fork, or vi- 
brating reed, one at each station. These reeds are attuned to the same rate of vi-^ 
bration, as nearly as may be. 

The motor, reeds, circuits, etc.. at each station, are shown in Fig. 255. c c are 
the vibrating reeds, a a are electro-magnets, the poles of which face the soft iroa 
teeth T rigidly attached to the periphery of the wheels w w'. These wheels i-evolve 
in a horizontal position, consequently they are meant to be shown in top, not side 
view, in the figure. Directly above the wheels ww' is placed a disc d, on which are 
shown certain segments, indicated by the numerals 9, 10. The teeth T are shown 
as extending beyond the periphery of the disc d. The shaft on which w revolves 
passes vertically through a hole in the center of disc d. On this shaft is rigidly 
fastened a strip of metal e, from the outer end of which droops a metallic brush, term- 
ed a "trailer." As the wheel revolves the trailer is swept over segments, 9-10, and 
also over other segments not shown in this figure. 

336 



SYNCHRCNOUS MULTIPLEX TELEGRAPHY. 



337- 



The reeds c c are kept in vibration in a well-known way. That is, when the 
reed is placed against the contact point p the resistance r is cut out, or short-circut- 
ed, and battery B exerts its full srrength. This magnetizes the electro-magnet m; 
hence the reed is attracted towards contact point p'. As now the circuit of u is- 
broken at p the resistance r is again placed in circuit, diminishing the current, mag- 



FIG. 255. 







CONNECTIONS — DELANY MULTIPLEX TELEGRAPH THEORY, 

net M loses its attractive force and reed c is withdrawn, by its own tension, to contact: 
point p, and so on, thereby producing the well known *' buzzer " action. 

Whenever the reed makes contact with p' the circuit of battery b' is closed. This 
magnetizes electro-magnet A. When the reed leaves contact p' the circuit of battery 
b' is opened and a is demagnetized, s and s are high resistance coils, shunted like 
r r\ across or around the contact points to prevent sparking. The uses of the other 
apparatus will be referred to presentl}^ 

The wheels WW, not being self-starting, are first ''flipped" into motion by an 
attendant. They are then maintained in motion as follows: (We may, for simplicity,, 
consider only the case of one wheel, the action of both being similar.) The 
teeth on the wheel, as it rotates, pass in close proximity to the curved polo -pieces of 
the electro-magnet A, which is in the circuit controlled by the vibrating reed ^i. At 
each full vibration of the reed the electro-magnet is momentarily magnetized and.. 



338 AMERICAN TELEGRAPHY. 

during the time it is thus magnetized, it attracts towards its poles two of the soft iron 
teeth of the revolving wheel. The momentum of the wheel carries those teeth slightly- 
past the poles of the magnet and brings another pair of teeth up to the poles, ready 
to be acted upon by them when the electro-magnet is again momentarily magnetized. 
In this way the wheel is not only kept revolving but it is also kept revolving at a 
uniform rate of speed as long as the magnetic pulsations of the electro-magnet a are 
uniform; for, if the last magnetic pulsations should accelerate the momentum of the 
wheel to the extent that it should tend to pass by the poles of the magnet, out of its 
regular time, the magnet acts as a drag upon it, the wheel, holding it back slightly. 

It would, however, be impossible to procure two reeds or tuning forks capable of 
vibrating in perfect unison, especially when at any distance apart, for any length of 
time, no matter how skillfully made, owing to variations in temperature, etc. Hence, 
in order to secure practical synchronism, some means, in addition to the ordinary nat- 
ural vibration of the reeds, or tuning forks, must be employed. 

The arrangement used for accomplishing this result in the system under consid- 
eration is shown in Fig. 255 also. The three segments marked 9, on disc d, at x, are, 
it will be seen, connected together and thence the circuit leads to a battery, Bg and 
to earth. Three segments marked 10, are also joined together and thence are led to 
and through a relay cr, termed a "correcting" relay, to earth. Segments marked 9 and 
10 are connected in a similar way on the disc at y, the only difference being that the 
" live " segments at the respective stations are at relatively different points of the 
disc, as shown in the figure. (The segments which are not connected to battery b^, or 
to relay cr, are termed "dead " segments; those that are so connected are termed, 
"live " segments.) 

Assuming the trailer at x to be on a " dead " segment, 9, while the trailer at y is 
on a "live" segment, 9, it is evident that no current can pass from battery b^; and 
further, it will be found, on examination that, so long as the trailers are on correspond- 
ing segments at x and y, no current will pass from battery b^ at either end, to the 
line. When, however, either of the trailers is driven faster than the other^ as, lor 
instance, if, as shown in Fig. 255, trailer at x should run so that it passes over a "live" 
10, while the trailer at y passes over a " live " 9, a current from ba.ttery b^ at y will 
pass over the line wire and through the correcting relay ce, at x, to earth ; thus mo- 
mentarily magnetizing that relay, which attracts its armature, opening the local cir- 
cuit of LC, as in figure. This permits the armature of relay d to fall back, opening 
the shunt around the battery b and allowing that battery to magnetize the electro- 
magnet RM, between the pole-pieces of which the lower end of the vibrating reed c, 
oscillates. The effect of the introduction of this magnetic field in the path of the 
reed is to retard its vibration and, consequently, the rate of pulsations transmitted 
to the motor magnet a is diminished. From what has been said it follows that the 
speed of the revolution of the wheel at x is retarded until it is brought into unison 
with the wheel at y. When, on the contrary, the trailer at y runs ahead of the trailer 
at X, " correcting " currents are similarly transmitted, from x, to the correcting relay 
cr', at Y, with equivalent result to that just described. 

In practice the " live " segments 10 are made somewhat broader than segments 
9, so that corrections will always be sent out from one or the other end before the 



339 



Ciji|i|i|i{i|i|i|i|i|i{-^|i|i|i|i{i{i{i|i{i|i{i 



o o 

^ .54.521654^^ 






O O 



N-C r-il 



dl 



I III I I I iKi I I I 



V 




340 AMERICAN TELEGRAPHY. 

loss of synchronism of the trailers can proceed so far as to interfere with signals on 
the segments which, as will presently be shown, are assigned to the transmission of 
despatches. 

This method of obtaining synchronism is adapted to the requirements of a multi- 
plex telegraph system as shown in Fig. 256. In this figure the disc d is shown with 
84 metallic segments, each insulated from the other. Assuming that it is desired to 
transmit six messages simultaneously, 72 segments are set apart for the purpose, and 
each of 6 desks at each end of the line is alloted 12 segments, as in Fig. 256. That 
is, starting, for instance, from a given point, as x^ on the disc, the first segment is 
given to desk No. i, the second segment to desk No. 2, at each end of the line, and 
so on, to the sixth segment. Here the two segments numbered 9 and 10 are skipped. 
A second and a third series of segments are then connected to desks Nos. i, 2, 3, 4, 5, 
6, when another two segments, 9 and 10, are again skipped and so on around the 
disc, as in the diagram, each desk being connected with different segments. 

As the wheel w revolves the trailer is swept over the segments in rapid suc- 
cession. The trailer makes about three revolutions, per second. It thus comes in 
contact with 216 desk segments per second and hence each desk at each end of the line is 
connected to the line 36 times per second. As an operator cannot make a dot in 
less time than, say, one-twelfth of a second, it follows that, during that time, the. 
trailer will have given him contact with the line thrice. If, for instance, the opera- 
tor at desk. No. 2, at x should hold his key closed for one second, 36 pulsations of 
electricity would reach the receiving instrument at desk No. 2, at t. In this way 
each of the 6 operators at each end may transmit messages as though he had entire 
control of the line. 

It necessarily ensues from this arrangement that each character sent from any 
one desk is formed of a num.ber of pulsations, and as such a condition of trans- 
mission would render signals unintelligible if the ordinary Morse relay and its local 
connections were used, a modification of that method is employed in this synchronous, 
system. There are two such modifications used in practice. One consists of the use 
of polarized relays, R, Fig. 256, as receiving instruments, and of pole-changing keys, 
K, ijs transmitters. When a key is open, let it be supposed that it places a positive 
pole of battery to line and that so long as these positive pulsations are received in 
the distant polarized relay, its armature remains on the ''dead," or back stop, 
point, and the local circuit is open. When the key is closed, negative pulsations will 
then be transmitted, and these will reverse the magnetism of the relay, and, hence,, 
its armature will be attracted to the other side and placed against the contact point,, 
closing the local circuit and sounder, the latter not shown. 

The polarized relay is chosen because, owing to its permanent magnetism, its ar- 
mature will remain passive on whichever side it is last placed, and until a reversal 
of polarity takes place in the core. 

Since the pole-changing key continues to send out pulsations whether it is open 
or closed, some means must be employed to take it out of the Avay when it is de- 
sired to receive messages on its corresponding desk. This is accomplished by chang- 
ing the position of a 3-point switch s, which in one position, throws the battery to the 
line and, in the other, places the line to earth. When midway between either stop it 



SYNCHRONOUS MULTIPLEX TELEGRAPHY. 



341 



opens its particular desk circuit. A disadvantage of this method is that a sending 
operator has no me'ans of knowing when he is being broken by the receiving operator 
until he switches in the polarized relay. 

Another method of availing of these pulsatory signals is that shown in Fig. 
257, in which the Morse neutral relay, NR, is employed, the contact point of which 
is placed on the back stop. In this case 110 pulsations are transmitted when the key 
is closed. But, when open, pulsations may pass from either end. This is due to the 

FIG. 257. - 







SYNCHRONOUS MULTIPLEX SYSTEM ARKANGED FOR '* NEUTRAL " RELAYS. 



arrangement of connections on the armature levers of f f'. Both ends, x, y, of the 
circuit, and the apparatus for one desk, are shown in the figure, also a few segments 
of the disc at each end. The trailers t t , are assumed to be passing over corres- 
ponding segments. Key k, at x, is shown closed, key k' at y, open. Thus pulsations 
from battery b' at x are transmitted over the line and are received in the neutral 
relay nr. These cause the armature of that relay to vibrate between its front and 
back stops so rapidly that the repeating sounder es does not respond, but remains 
against its upper stop, thereby closing the local circuit of the reading sounder s. In 



342 



AMERICAN TELEGRAPHY. 



this way the pulsatory signals are caused to produce, at the receiving end, ordinary 
dots and dashes in the sounders. 

The pulsatory currents received at the relays are augmented and prolonged by 
the condenser c or c/ placed around the relays. The action of the condenser in perform- 
ing this function may be stated as follows : During the existence of a pulsatory 
current the condenser is charged and upon the cessation of the charging current the 
accumulated charge is discharged through the relay in a direction similar to that 
of the current which had charged the condenser. 

FIG. 258- 




SYNCHRONOUS MULTIPLEX SYSTEM : ARRANGED FOR LONG CIRCUITS. 



A very d3cided improvement in the Avorking of the relay is noticed when the 
condenser is employed. The usual resistance of the neutral relays now used in this 
system is about 1,000 ohms. The arrangement of transmitters, f, r' is useful, inasmuch 
as it places the receiving relay to the line every time the operator closes his key, thus 
enabling him to hear breaks from the distant end. 

As previously stated, it is well known that on long telegraph wires a perceptible 
time is required to discharge the wire of the electricity with which it has been charg- 
ed in the transmission of signals. This conduces to retardation of signals, which, if 
not guarded against, would, in systems of the nature just described, tend to produce 
*' false " signals in the receiving instruments, for, otherwise, the charge remaining in 



SYNCHRONOUS MULTIPLEX TELEGRAPHY. 343 

the wire from one signal would be received in the instruments connected with the 
succeeding segments. 

In the operation of the Delany synchronous system, just described, provision is 
made for dispersing the charge accumulated in the wire from previous signals, and 
which, if not dispersed, would not only tend to produce false signals in the signaling 
relays, but would also interfere with the synchronism, by sending curients through 
them at inopportune moments. The devices for carrying off the accumulated charges 
consist of metal segments, not seen in the diagrams, placed between each " desk" seg- 
ment. These are all connected together and then grounded; thus permitting the re- 
sidual electricity in the wire to escape harmlessly at both ends of the line. 

On circuits of moderate length, say, about loo miles of overhead wire, this de- 
vice is found quite efficient, but on longer lines not to the same extent, owing to the 
greater delay in charging and discharging the wire. 

To permit the use of the system on longer circuits, the arrangement of transmit- 
ters and segments shown in Fig. 258 has been devised, and has been found of utility. 

In this modified arrangement advantage is taken of "retardation'' in the fol- 
lowing manner. In the figure x and y represent the terminal stations, with trailers 
TT, segments, etc. The electrical synchronizing devices remain as before. The chief 
change consists of a transposition of the segments by means of a specially construct- 
ed transmitter e, so that, when the trailer at the sending end, say, x, in the figure, is on 
a segment connected with the battery, the trailer at the distant station is on a seg- 
ment connected to the ground, as at y. This carries off so much of the charge as 
may have reached y. The next instant the trailer at x passes to a segment connected 
with the ground, via the transmitter e, and through a rheostat r; this cuts off all 
battery ; at practically the same instant the trailer at y passes over a segment con- 
nected with the relay nr', whereupon the retarded charge passes through the relay 
and actuates it. In the same way signals are also sent from y to x. 

The local circuits of the neutral relays remain as before described. 

In view of the fact that the chief drawback to the operation of systems of the 
synchronous order on long lines is due to the difficulty in adjusting the apparatus to 
meet conditions set up by the attempt to work the system from both ends, simultan- 
eously, Mr. Delany proposes to assign one or more wires to be used in transmitting 
signals exclusively in one direction, by which arrangement it is believed the matter 
of adjustment would be much simplified and the efficiency of the system thereby 
largely enhanced. 

The foregoing described system somewhat modified is in successful operation in 
Great Britain. 

A feature in connection with synchronous telegraph systems, uncommon in other 
systems, is that, during foggy or rainy weather, they have been found to work much 
better than during dry weather; the inferior insulation of the wires during wet 
weather apparently aiding in the dispersion of the charge remaining from previous 
signals. 



CHAPTER XXII. 



the telephone— simultaneous telegkaphy and telephony. — vakley-athearn du- 
plex or diplex. the edison phonoplex. 

The Telephone. 
A detailed description of the telephone, in theory and practice; its apparatus, 
xjonnections, etc., would furnish matter for a book of no small dimensions, if devoted 
^exclusively to that purpose. It is, therefore, not feasible to enter into a lengthy ac- 
count of the practical operation of the telephone, in this work, as to do so would unduly 
extend its proportions. A brief description of the principle of the telephone will, how- 
ever, be given here. 

FIG. 259. 





THEORY OF TELEPHONE. 



In the act of speaking, air vibrations are set up by the voice. These vibrations con- 
sist of to and fro motions of the air particles, which vibrations so act upon the ear 
nerves as to produce the sensation of hearing. 

The electrical telephone consists of a '' transmitter," by means of which the air 
vibrations, originated by the voice, are caused to develop electrical vibrations in a 
conductor, or, stated in another way, variations of electrical current strength, which, 
in turn, establish corresponding variations in the strength 'of a magnetic field, 
^whicli latter variations produce vibrations in a diaphragm which are practically sim- 
ilar to those originated by the voice at the transmitter. 

A simple arrangement of apparatus for effecting the foregoing results is shown 
in Fig. 259. MP is the mouth-piece of a transmitter; td represents a flat disc, or 
diaphragm shown end on. At its center a small platinum contact point p, is attached. 
<j is a small piece of carbon, held lightly, by suitable means, against p. These con- 

344 



THE TELEPHONE. 345 

Stitnte the "transmitter " of the telephone. b is a battery. A line wire is connect- 
ed to c. A magnet m is placed in the circuit at the receiving end. Opposite m a me- 
tallic diaphragm rd is placed within an ear-piece ep. 

In the transmission of speech by this method the mouth of the speaker is placed 
adjacent to MP; the ear of the listener to ep. Both of thediaphragnibareheld some- 
wliat rigidly at their edges by suitable devices, and they tend to assume a certain po- 
sition to which they return by their own tension if displaced by any means. 

It is known that the electrical resistance of carbon varies under pressure; that 
the strength of current in a circuit varies with tlie resistance of the circuit; that 
the magnetic field of an electro-magnet varies with the strength of current in its 
coils, and that the armature (such as kd) of an electro-magnet tends to vary its po- 
sition, when free to move, with variations in the strength of the magnet. 

Remembering these points the principle of the telephone will be readily under- 
stood. 

The circuit in Fig. 259 is from the ground at the left, through the battery b to 
the platinum point p, to and through the carbon to the line wire, thence to the mag- 
net m and the ground, at the right of figrure. 

When speech is uttered into the mouth-piece air vibrations are set up which 
" strike " against the diaphragm td. This gives the diaphragm a to and fro motion 
irhich alternately increases and decreases the pressure of p against the carbon c, with 
the result that the resistance of the carbon is varied to a greater or less extent, de- 
pending upon the amplitude of the vibrations of the diaphragm. Consequently, the 
strength of current due to the battery b is varied in accordance with the variations 
of the resistance at c. These variations of the current strength, again, vary the 
magnetic strength of magnet m in manner proportionally equal to the variations of 
the current strength ; hence, the diaphragm rd, which in this case acts as the arma- 
ture of M, is given a to and fro motion, of greater or less amplitude, corresponding 
with the variations in the field of the magnet m. These vibrations of the *' receiving " 
diaphragm set the air particles in its vicinity into vibration, which air vibrations, in 
turn, entering the ear of the listener reproduce therein the words, or sounds, uttered 
at the mouth -piece of the transmitter. 

In practice the transmitter battery is placed in circuit with the primary of 
an induction coil (as shown in figures following) , the secondary coil being placed in 
the main line circuit. This arrangement is found to augment the volume of the re- 
ceived signals. 



Simultaneous Telegraphy and Telephony. 

By simultaneous telegraphy and telephony is meant the dual transmission of 
telegraphic and telephonic signals over the one circuit. 

If a telephone " receiver " be placed in an ordinary Morse telegraph circuit, a 
loud crackling noise, due to the rapid and, comparatively, powerful vibrations of the 
diaphragm produced by the makes and breaks of the telegraph circuit, is heard in the 
receiver. 

It is therefore evident that, before simultaneous telegraphy can be rendered pos- 



346 



AMERICAN TELEGRAPHY. 



sible, the noises in the receiver, due to the causes stated, must be obviated; otherwise it 
would be impossible to hear, intelligibly, the telephonic signals. Tliis requirement 
has been met in several different ways, but, probably, the most successful is that due 
to Van Rysselberghe, who gets rid of the noises in the telephone by the introduction 
of apparatus into the circuit which " graduates " the rise and fall of the "telegraph " 
currents at . the time of make and break of the telegraph circuit. The effect of thus 
graduating the telegraph currents is to produce in the diaphragm of the telephone 
receiver a gradual movement, to and from its electro-magnet, which movement is not 
sufficiently rapid to cai;se an appreciable sound. Upon this gradual vibration, or in- 
flection, of the diaphragm, is superposed the rapid vibrations due to the vibratory cur- 
rents originated by the transmitter of the telephone. 

To obtain the desired gradual rise and fall of the telegraph currents Van H 's- 

FIG. 260. 




selberghe utilizes the retarding and prolonging effects of the self-induction of elec- 
tro-magnets in an electric circuit, in a manner to be described presently. 

An idea of the manner in which the vibrations due to the telephone transmitter are 
superposed upon the inflections of the diaphragm due to the telegraphic signals may be 
gained by a consideration of the ingenious mechanical illustration, Fig. 260, devised by C. 
F. Varley to show the principle of a simultaneous ''telegraph and pulsatory" current sys- 
tem invented by him. In that figure r is a rope drawn over the pulleys p p, and stretched 
tightly by the weights ww. The smaller pulleys // are held, loosely, over the rope k. It 
is plain that when the rope is moved to and fro, longitudinally, one weight will rise while 
the other falls, and that by a pre-arrangement of the frequency or duration of the 
movements of the weights, up and down, signals might be transmitted, during the 
transmission of which signals the small weights would be practically stationary. If, 
however, while the rope is being moved to and fro, as stated, the rope be hit with a 
hammer, it will be set into rapid vibrations which will cause the smaller pulleys to 
dance while the vibrations last; but these vibrations will not interfere with the reception 
of signals by the rise and fall of the weights. If, also, the frequency and duration of 
the strokes of the hammer upon the rope be pre-arranged, signals which would be due 
to the *' pulsatory " motions of the rope might also be transmitted. 



SIMULTANEOUS TELEGRAPHY AND TELEPHONY. 



347 



The Van Rysselberghe devices to effect the silencing of the telegraphic signals 
in the telephone receiver consist of condensers and electro- magnets, or magnetic coils, 
inserted in the telegraph line, outside of the telegraph instruments, as shown in Fig. 
261. In this figure R is the relay, A the key, and B the main battery, of the Morse 
system, g g are magnetic coils, termed " graduators ". In order to increase the re- 
tarding and prolonging effects of the coils, an outer shell of soft iron is placed over 
them, in addition to the usual iron core. To obtain absolute silence in the telephone 
receiver, so far as the telegraphic signals are concerned, the resistance of the magnetic 
coils should be about 500 ohms each, but practical silence can be obtained with half 



FIG. 261. 



(g: 



J 



W 



^=(]^^ 



L.ine' 



^ 



i 






that resistance.* c care condensers which assist in rendering the rise and fall of the 
telegraph currents gradual. 

As it is necessary that the telephone circuit should not at any time "ground" 
the telegraph circuit, the telephone apparatus is " separated " from the main line, 
but yet electrically connected thereto, through the medium of condenser e, which 
acts, practically, as a separator and a "repeater," conveying or relaying, the tele- 
phonic signals, by induction, from the main line to the telephone receiver. 

The general theory of the operation of simultaneous telegraphy and telephony 
may be briefly outlined as follows : Assuming, for example only, the strength of the 
" telegraph" current to be 2,000, and that of the telephone current to be i. If, while 
thediaphragmof the telephone receiver is attracted, or in proceess of gradual attraction, 
by a telegraph current, of, say, positive direction, a "telephone" current of similar di- 
rection be transmitted, the current will be suddenly increased to 2,001 and the dia- 
phragm will be given a sudden minute impulse towards its magnet. Should then a 
negative telephone current follow (the telegraph cuiTent remaining as before) the cur- 
rent on the line will be suddenly reduced to 1999, and thediai>hragni by its own ten- 
sion recedes rapidly from its magnet. In the actual operation of these systems, of 
course, many hundred pulsatory, or undulatory, currents, might be transmitted during 

* With the new form of retarding coil now used, in which tlie core is a dosed iron ring, 50 ohms suffice. 



348 AMERICAN TELEGRAPHY. 

the time taken to transmit one telegraphic signal, and thus, while the diaphragm is 
being gradually attracted to, or is gradually receding from, its magnet, owing to vari- 
ations in the telegraph current, at the same time it may be making several hundred 
intermediate forward and backward motions of less amplitude, due to the variations 
of the line currents caused by the telephone transmitter. Of course the minute addi- 
tions to or subtractions from the telegraph current are not noticeable on the telegraph 
instruments. 

In Fig. ,'262, A may be supposed to represent the undulatory or graduated telegraph 
current, b the quick and minute, or undulatory, current transmitted by the telephone 
transmitter, and c the combination of the two. 

By the foregoing stated expedient of rendering the makes and breaks of the tel- 
egraph circuit gradual, to such an extent that they are not noticeable in the telephone 

FIG. 262. 




ri VV\A/\/VV\AA/V\A/V\/V/\AA/\/V\A/UW\AAAAAAAAAAAAA^^ 



^^uuvyvv^ ^^^Www^^^ 



receiver, the telephonic signals may be, and in practice are. superposed upon the teles^ 
graphic signals and heard in the telephone receiver, virtually, as though on a separate 
circuit. 

In Fig. 263 is given a theoretical diagram of the connections and apparatus at 
two stations of a combined telephone and telegraph circuit. The wires No. i and No. 
2 represent two Morse circuits. Rj^ and Rg, and Kj^ and Kg are the relays and keys of 
those circuits, and mb, mb' are the main batteries feeding both of the Morse circuits, 
in the well known way. The "graduating" instruments are shown between r^ and 
P in circuit No. i and between Ro and f^ in circuit No. 2. These instruments con- 
sist of condensers c, of about 6 microfarads each, as marked, and of the magnetic 
coils GC, of about 50 ohms each. 

The "telephone" systera, which comprises the transmitters tt; receivers tV, bat- 
teries TB, etc., utilizes both of the telegraph circuits, as a "metallic,'' or round circuit. 
It will be seen that the circuits, No. i and No. 2, are not metallically connected by 
the wires of the telephone system, but are electrically connected through the " separ- 
ating " condensers sc, which instruments, as already said, virtually act as repeaters of 
the rapid pulsations set up by the transmitter of the telephone; the minute and 
rapid variations of potential caused by that transmitter being reproduced at the ter- 
minals of the condensers and, consequently, also reproduced on the main line circuits 
on both " sides" of the condensers. 

When it happens that there are " intermediate " relays in the telegraph circuits 



SIMULTANEOUS TELEGRAPHY AND TELEPHONY. 



349 




mm^ 



increasing the clearness and strength of received signals. 



it is necessary to " shunt" 
those relays with conden- 
sers, as shown in the case 
of the " Yarley- Athearn " 
duplex and the "Edison" 
phonoplex, next described. 

In Fig. 264 the actual 
connections of the gradu- 
ating apparatus are shown. 
In practice the magnetic 
coils Gc and condensers c 
of the graduators, are, 
for convenience, placed in 
one box g, and the termi- 
nals are brought to the 
outside of the box, as 
indicated. The resistances 
and capacities of those in- 
struments are plainly mar- 
ked in Fig. 263.* 

The arrangement of the 
telephone apparatus, as 
shown in Fig. 264, is vir- 
tually that used in "long 
distance" telephony in this 
country. The apparatus 
consists of an induction 
coil u; an annuciator, or 
vibrating bell i, which 
operates in response to a 
distant "call," a trans- 
mitter T ; transmitter bat- 
tery TB, about 2 volts; 
an automatic circuit clo- 
ser and opener f; a tele- 
phone receiver tr and a 
small switch s, which,when 
depressed, short-circuits 
the secondary coil ;;/ of 
the induction coil, thus re- 



movino- 



th( 



maornetic 



resistance of that coil from 
the circuit and thereby 



* Experiment will show whether one or more graduating coils and condensers are essential to a particular circuit, and 
also the amount of retardation and capacity necessary for best results. Inductance coils e e placed around t t' as shown 
are serviceable in preventing interference between Morse circuits. 



350 



AMERICAN TELEGRAPHY. 



For the purpose of " ringing up ' ' the distant station, a vibrator or " generator/* 
may be inserted at x. 

The practical operation of the switching apparatus k, etc., in sending and re- 
ceiving, may be briefly described : As shown in the figure, the telephone receiver 
weighs down the hook, or switch k, thereby opening the transmitter battery, and 
putting into circuit the annunciator magnet i, in readiness to receive a call. When 
the receiver is lifted from the hook, the latter, raised by the spring /?, opens the an- 



no. 264. 




TERMINAL CONNECTIONS— TELEPHONE, ETC. 



uunciator circuit at n and closes the circuit of the receiver at the strips/. This, it 
will be seen, places the transmitter, and battery tb, in the circuit of the primary 
coil p of ic. 

Simultaneous telegraphy and telephony has been in successful operation in differ- 
ent parts of Europe.* Prolonged experiments in this country have demonstrated that 
the combination of the two systems can be operated on circuits of 1,000 miles in 
length. In other words, on any circuit, where simple telephony is feasible, but it 
has been found also that the " graduating " apparatus is more or less detrimental to 
duplex and quadruplex telegraphy, especially the latter. 

* Simultaneous telegraphy and telephony is now being successfully carried on in this country. 



varley-athearn duplex-diplex. 
Varley-Athearn Duflex-Diplex. 



351 



This is one of several aiTangements, of which the first was devised by C. F. Yar- 
ley, to increase the capacity of a wire by superposing "pulsatory" current signals upon 
the regular Morse signals. 

To accomplish this result successfully it is necessary, as in simultaneous telegraphy 
and telephony : First, that the pulsatory currents shall not be so powerful as to actuate 
the Morse relays. Second, that the pulsatory receiving apparatus shall not respond to 
the regular Morse signals. 

FIG. 265. 




VARLEY-ATHEARN "SUPERPOSED" CURRENT SYSTEM. 

The first requirement is met by the use of apparatus which sets up momentary cur- 
rents of comparatively feeble strength. These currents may consist of a single pulsa- 
tion for each character of a signal, as in the Edison " phonoplex " (next described), or 
each character may be composed of a number of such pulsations, as in the Varley 
Athearn device, now being considered. The second requirement is met by the use of 
receiving apparatus of such a nature, or so placed in the circuit, that it will only re- 
spond to quick, momentary pulsations; and also by taking advantage of the fact, as is 
also done in simultaneous telegraph and telephone systems, that currents which would 
otherwise rise and fall abruptly, are retarded in passing through an electro-magnet, or 
a "magnetic " coil, and, consequently, rise and fall gradually, and thus do not afl'ect 
the receiving apparatus of the pulsatory current system. 

The Varley-Athearn arrangement, for the purpose stated, is shown, theoretically 
in Pig. 265, in which two terminal stations, x and Y^are represented. 



352 AMERICAN TELEGRAPHY. 

The Morse apparatus consists of the relays re, keys kk, and sounders ss. ^ib is the 
Morse battery. The "pulsatory " apparatus at x consists of a magnetic coil em, of a 
resistance of 15 or 25 ohms. The core of this coil is generally composed of a number 
of fine, soft iron wires, b is a vibrating reed, or buzzer, vb is a battery, which mag- 
netizes the coil EM, in certain positions of the reed r. t is a transmitter, operated by. 
key KT. 

At Y, the " pulsatory " apparatus consists of a sensitive, short core relay sr, with 
contact on back stop, and condenser, pc. 

The " pulsatory " currents are set up by the action of the vibrating reed of the 
buzzer, which is kept in vibration in the usual way i^see Buzzer). When the reed is 
against its contact i the coil em is magnetized. When the reed leaves contact, i, the 
coil in demagnetizing " discharges " into the line a, if the transmitter t is in the position 
shown in Fig. 265. When the transmitter is closed, the pulsations are cut off from the 
line, the wire cw, via which the pulsatory current set up by the coil would pass to the 
line, being then open. As long, therefore, as the transmitter is open, the vibratory cur- 
rents pass to the line, and reaching the distant end (y) cause variations in the charge 
of the condenser pc, which " charges," in turn, cause the armature of sr in the con- 
denser circuit, to vibrate, back and forth, against its stops. (In this case, also, the con- 
denser SR may be supj^osed to act as a " repeater " of the pulsatory current). 

While that armature is thus rapidly vibrating the local sounder s' is open, inas- 
much as its comparative sluggishness prevents it from following the rapid vibrations of 
the armature. When the armature ceases vibrating it rests on its back contact point 
and closes the local circuit of s'. Since the pulsatory currents are only permitted to 
reach the line when the transmitter at x is open, and the sounder s' at y is closed only 
when the armature of sr is on its back stop, it is clear that the signals received on that 
sounder will be on the front stroke, and since, while the vibratory signals are passing 
in the relay sr, the sounder s' is closed, and vice versa, it is evident that the opening 
and closing of the transmitter will have the effect of producing the usual dot and dash 
signals in the sounder s', (as, for example, in the case of the pulsatory signals of the 
synchronous multiplex system, when the Morse lelay is employed). 

The Morse signals from x are made comparatively gradual, or are "graduated," by 
being caused to pass through the Morse relay r, and, when the transmitter is open, 
through the coil em; consequently, SR, at y. is not actuated by the Morse signals, the 
currents thereby set up in the circuit of condenser pc not being of sufficient force to 
effect that result; and, on the other hand, the variations in the strength of the Morse cur- 
rents, due to the coil em, are not of sufficient strength to affect the Morse relays. The 
condenser c', across key k' and r, at x, tends further to "graduate " the Morse signals 
and also, practically, keeps the pulsatory circuit closed when that key is open. Con- 
denser c is employed chiefly to diminish the spark at the contact points i when the cir- 
cuit of VB is broken. As the transmitter t is " continuity-preserving," the Morse cur- 
rents pass to the line regardless of whether that instrument is open or closed. 

This arrangement, it will be seen, is more than a duplex and less than a 
quadruplex, since two messages may be sent out from station x at once, or one 
from station x and one from station y, simultaneously. The operator receiving the 
pulsatory currents signals at y is furnished with a key, ks, whereby he breaks the dis- 



THE EDISON PHONOPLEX. 



353 



tant sender, by way of tlie Morse circuit. It would be quite possible to equijD y with 
" pulsatory " transmitting apparatus similar to that at x, which would then give the 
practical equivalent of two single wires, but as the system requires somewhat expert 
attention, it has not hitherto been so arranged, chieflj^ perhaps, because such attention is 
least available where the use of such a service would be most advantageous, as, for ex- 
ample, in branch offices. 

Experience has shown that this device is much better adapted for short, than long 
circuits. 



The Edison Phonoplex. 

This system was also devised to extend the facilities of existing wires by superpos- 
ing pulsatory siguals upon regular Morse circuits. It is in service on a number of 
railroad wires in this country. 

FIG. 266. 




z. 



ine^ 



L^TTW^ 



EDISON PHONOPLEX-THEOKY. 

A theortical diagram of the system is given in Fig. 266. In that figure, r and k 
are the ordinary Morse relay and key. m is a coil of wire wound upon an iron core 
formed of a bundle of fine iron wires. It is employed to originate pulsatory currents 
when the phonoplex key x, is opened and closed, p is an instrument termed the 
"phone." It comprises an electro-magnet, opposite the poles of which is placed, in a 
horizontal position, a metallic disc d^ somewhat similar to the diapjn-agmof the Bell 
telephone receiver. T is a transmitter of special construction, having several functions, 
one of which is to short circuit the phone; the object of which will be mentioned pre- 
sently. Key x operates transmitter t, and the latter opens and closes the phonoplex 
Lattery, b. When lever a of key x is open, in the sense that the ordinary telegraph 
key is open, the bent lever f is away from the contact F,' and the phonoplex battery b 



354 



AiMERICAN TELEGRAPHY. 



is open, and the "magnetic" coil m is short-circuited via the wires 5, 6, 7, 8 and the 
lever of transmitter t, the latter instrument being also closed when key x is closed. 
When lever r of x is placed in contact with r', it slips out of contact with x. The con- 
tacts f' and X are insulated from the metal framework of the key. The lever f is 
electrically connected with that framework. 

When transmitter t is open, as in Fig. 266, the phone is thrown into the main line 
circuit, as may be seen. 

c is a condenser placed around the key K and the Morse relay R. A similar con- 
denser is placed around the other relays in stations between the terminal stations of 
the phonoplex circuit. Its function is to keep the circuit practically intact for the 
transmission of the pulsatory signals during the operation of the key k. It also facili- 
tates the passage of those signals past the relay r (it being known that electro -magnets 
in a circuit tend to retard rapid pulsatory signals). A condenser is placed simi- 
larly around the other relays in stations between the terminal stations of the phonoplex 
circuit. The condenser c', placed around the coil m, prevents excessive sparking at the 
contact points A A of the transmitter t. It also facilitates "incoming" signals on the phone. 
In the operation of this system, also, it is necessary that the phone p should not be 
seriously affected by the makes and breaks of the Morse circuit. This is more or less 
successfully accomplished by the use of the condenser around the keys, which has a 
noticeable effect in diminishing the abruptness of the "rise and fall" of the Morse cur- 
rents on the line. The relays in the circuit also aid in " graduating " the rise and 
fall of the telegraph currents. 

The phone is provided with an adjusting gear g, by means of which the poles of 
the electro-magnet of that instrument are withdrawn from thediapln-agmto a point just 
beyond the active, or harmful influence of the regular Morse signals, but not out of the 
influence of the pulsatory ciyi^ents. 

The " pulsatory " currents are originated by the charge and discharge of the coil 
M, brought about by the operation of transmitter t, which whether open, or closed, (and 
when the lever f of x is " open ") charges the coil m by the battery b. Between the open- 
ings and closings of the transmitter the current of self-induction of the coil discharges 
into the line, thereby actuating the distant phone. 

The pulsatory currents must be of such a strength as not to affect the Morse relays 
on the line, but at the same time must be sufiiciently strong to quickly '' flip ",the dia- 
phram of the phone. The current set up by the magnetic coil gives, on the phone, a 
fairly loud signal, which is enhanced by attaching, close to the diaphragm a small, split 
metal ring /, which dangles loosely on the diaphragm. 

It is obvious that it would be difiicult to read these signals if something were not 
done to distinguish between the up and down "strokes." By the use of a small resist- 
ance coil k', which, by means of the transmitter t, is placed in the circuit of the phono- 
plex battery b, at, or just before, the time corresponding with the signal made on the 
up stroke, and this has the desired effect of making quite a distinction between the two 
strokes. It does so by diminishing the strength of current in the magnetic coil circuit. 

The battery b used for this purpose has generally been a " quick-acting ' ' bat- 
tery, such as a bichromate of potassium battery, of from 612 cells. Of late the Edi- 
6on-Lalande battery has been successfully employed for this work. 



THE EDISON PHONOPLEX. 



355 



FIG. 267. 



It is further evidcDt that, if the phone p were left in the circuit at all times, it 

would be operated by the home magnetic coil when the latter was being actuated by 

the home battery b, and would, in consequence, give out a disturbing sound at siicli 

times. Means are therefore provided for cutting 
out the phone to avoid this defect. These means 
consist of the lever i. and contact pin c on trans- 
mitter T, which contacts, it is seen, are open in 
the figure, leaving the home phone in the main 
circuit, ready to be acted upon by the distant 
phonoplex, but, when the key x is closed, at which 
time the transmitter t closes also, l and c come 
together and short-circuit the phone by way of 
the wires 1 and 2, j s stated. 

The regular Morse signals on the main circuit 
having been rendered of no eifect upon the dia- 
phragm of the phone, the effect of the pulsatory 
current of the phonoplex circuit is either to 
ra])idly increase or decrease the Morse currents, 
virtually as in the case of simultaneous telegraphy 
and telephony, according as the pulsatory currents 
oppose, or co-operate with, the Morse currents. 
The variation in the strength of the Morse 
current thus produced will not operate the 
Morse relays, unless when the latter may be work- 
ing on a very fine adjustment, but, as has been 

said, the variation is sufiicient to operate the " phone." It may be added that having 

once "graduated " the Morse currents, or adjusted the phone, so that those currents 

are unfelt in the phone, it 

will make no difference in 

the practical working of the 

pulsatory system whether 

the Morse system is idle or 

working. 

In Fig. 267 the phone is 
shown as it appears in prac- 
tice. The magnetic coil is 
shown in Fig. 268. This 
system may be used on cir- 
cuits of from one hundred to 

one hundred and fifty miles in length, and it is not limited to any stated number of 
intermediate stations. Neither is it necessary that a continuous Morse wire be used., 
as the pulsatory signals may be transferred from one wire to another by connecting 
any desired wires together by a condenser. 




THE PHONE. 



FIG. 268' 




MAGNETIC COIL. 



355^ 



AMERICAN TELEGRAPHY. 



The Gray Harmonic 1 elegraph. 



It is known that a steel rod or a tuning-fork lieicl at one end will vibrate at a 
given rate when hit a smart blow, or moved out of the normal position and quickly 
set free. This rate of vibration of the rod or fork is termed the fundamental rate of 
vibration. If such a rod whose fundamental rate of vibration is, say, lo per second, 
should receive a blow, in a direction coinciding with its motion, every one-tenth of a 
second, it would continue to vibrate indefinitely. If, on the contrary, it should 
receive blows at intervals not in accord with its rate of vibration, some of the blows 
would op[)ose its motion and it would practically come to a standstill. 

' In Gray's harmonic telegraph system this general principle is employed. The 
theory of this ingenious system is shown in diagram, Fig. 268Z>. f\ f^, f^, F%.are 
circuit-breaking foi'ks, fastened at one end x^ which respectively pulsate the circuits 
of main batteries B^, B% B^, B*. These forks are attuned to given rates of vibration, 
S5iy 264, 320, etc., vibrations per second. When these forks! are set^in vibration 




they open and close the circuits of their respective main batteries at a rate corre- 
sponding with their fundamental rate of vibration. These forks are kept in constant 
vibration by well-known electromagnetic vibrating devices not shown in the figure 
{i<ee pages 257, 272, 2)2)^^ 357)5 while the system is in operation, but they can send 
out curi-ent pulsations to the line only when double transmitters t\ t% t^, t" are 
open, for it may be noticed that these forks short-circuit their respective main 
batteries at every vibration by way of the lower tongues ]) /?, etc., when their trans- 
mitters are open, and that the main battery is open at the lever of the transmitter 
when that instrument is closed, so far as the vibrator is concerned. In the figure 
T^ t'^ are open and therefore forks F^ F^ are transmitting pulsations to line by way of 
the levers and tongues / ^ of those transmitters. On the other hand, as transmitters 
T^ T'^ are closed the main batteries B^ l" are open at the levers of those instruments, 
and hence no pulsations pass from them to the line at this time, although, as stated, 
forks F^ F^ continue to vibrate as before. A weak current still goes to line, however, 
as will be explained shortly. The upper tongues t are insulated from the levers of 
transmitters t as indicated; the lower tongues are metallically connected therewith. 
At the receiving station B four electromagnets, f\ /^ /^ /\ are placed in the 
main line. The armatures of these magnets are reeds fastened at one end and attuned 
to vibrate at rates corresponding with their respective transmitting forks. Hence /' 
will only respond to current pulsations transmitted by f\ /" will only respond to 
those from f% and so on. Each of the reeds is equipped with a light lever (not 



THE GRAY HARMONIC TELEGRAPH. 35-^ 

shown) wbich rides loosely on the top of the reed. This rider is part of a local 
circuit in which there is an ordinary sounder. When the reed is at rest the local 
circuit and sounder are closed; when in vibration the sounder is open, as in the 
Varley-Athearn system, Fig. 265. Hence, by this arrangement, as the pulsations 
from the transmitting forks pass to line only when the double transmitters are open, 
the Morse signals transmitted by means of the keys controlling those transmitters are 
received on the front stroke. 

The batteries b', b% b^, b* are divided or tapped at a certain point such that when 
a transmitter is closed, as at T^ t', the larger portion of each battery is open at the 
lever of the transmitter, and that only the smaller portion is in the main circuit. 
This arrangement was rendered necessary by the great reduction of current strength 
caused by the rapid vibration of the transmitting forks, probably due to imperfect 
contact at the forks, and also to the effects of inductance of the numerous magnets — in 
other words, to the high impedance of the circuit. This decrease of current strength 
amounted in practice to about 60 per cent. For instance, if 40 volts maintained a 
required strength of current on the line when a transmitting reed was at rest, about 
100 volts were necessary when it was in operation. 

With this system there is also combined a duplex telegraph system, employing 
the single transmitter s, a differentially wound relay R and rheostat k at A, jind an 
ordinary Morse relay R, a double transmitters', and a resistance coil h at B. Trans- 
mitter s operates relay R^ by cutting in and out main battery b\ Transmitter s' 
operates relay R by cutting in and out the resistance H. [See page 265.) As the 
transmitter s' at B is only used to interrupt the distant sending operators, each 
receiving operator on the harmonic system is placed in control of s' by means of the 
keys shown. 

As it is found desirable in the operation of this system to maintain a nearly 
uniform current in the relays of the harmonic system, an adjustable resistance r"^ is 
attached to the line wire outside of /', and this resistance is thrown into the circuit 
simultaneously with the throwing out of the resistance H and vice versa. This 
diverts as much of the increased current due to the removal of h as may be required 
to effect the desired result. Nevertheless, the removal of the resistance 11 disturbs 
the line balance at A and thus operates relay R. {See Chapter XVI.) 

To prevent the operation of the relays R and r' by the pulsatory currents, their 
springs are adjusted to hold the armatures open over the maximum pull of those 
currents, and thus are only responsive to the additional battery b^, or to the variation 
in the balance of the line caused by inserting or removing the resistance H. Con- 
densers are placed across the terminals of relays R R', as shown at c, to permit the 
free passage of the pulsatory currents. 

No graduators are used in this system, and apparently they are not essential, for 
the reed armatures of the receivers of the harmonic system, being exactly attuned 
to the note of the corresponding transmitting forks, are not readily affected by 
pulsations that are not in unison with their rates of vibration. Furthermore, the 
large number of electromagnets in the circuit tend to round off the Morse telegraph 
signals. Six messages were simultaneously transmitted by this system, which was 
for a considerable time in practical operation on the lines of the Postal Telegraph 
Cable Co. between New York and Chicago on wires of one and a half ohm resist- 
ance per mile. Its use, however, was limited, not only by the care required in 
its adjustment, but also by the marked inductive effects of its pulsatory currents 
on parallel lines, which made it difficult to operate to any great distance more than 
one circuit equipped with this system, and even on short circuits some difficulty was 
experienced in working the system on more than one parallel wire. All of the 
circuits on which this system was operated have been abandoned and the quadruplex 
system substituted therefor. 



CHAPTER XXIII. 



Time Telegraph Service. 

The "Time" Telegraph which is in quite extensive use in New York City and 
vicinity consists in the transmission of pre-arranged electrical signals over circuits 
controlled by a standard clock to various offices of railway companies, jewelers, etc., 

FIG. 269. 




to 7}>rrce'Cu'Oulj^ 




TIME TELEGAPH SIGNALS-THEORY, 

and which signals are so arranged that, to the initiated, they indicate, by a single 
stroke, or strokes, of a sounder, or electric bell, the time to a second. 

These signals are sent out by the standard clock at the normal rate ©f one 
stroke every two seconds, excepting that, in each minute, the fifty-eighth second is 
omitted. Again, at twenty seconds before the beginning of every period of five min- 
utes the signals cease, etc. 

- 356 



TIME TELEGRAPH SERVICE. 



357 



Tlie arrangements for automatically transmitting these signals are outlined in 
Fig. 269. 

In this figure M is the second-hand of the standard clock. Its wheel w has 
twenty-nhie teeth, a thirtieth tooth being cut away, as may be seen. A delicately 
poised fiat rod c is placed in the path of these teeth, and as each tooth passes under 
the rod, tlie circuit in which the relay k is placed, is broken. The result is that, dur- 
ing each minute, the circuit is broken 29 times, but at the fifty-eighth second it is not 
broken. This indicates that the first beat after the pause is the beginning of the next 
miinite. The w^ieel hw is so geared as to make one revolution every five miinites. Its 
periphery is notclied for a distance equal to one-fifteenth of its circumference. A 
contact springs rides lightly on this periphery. Branch wires lead from this contact 
spring, and a fixed contact point s', to the relay circuit. When the notch in the wheel 

FIG. 270. 




arrives at a certain point in its revolution the flat spring s drops into it. This com- 
pletes, at s', a circuit through the relay. Hence so long as the spring s remains in the 
notch the second-hand wheel w cannot open the relay circuit. The notch on hw is so 
arranged that it arrives at the point opposite the spring s at exactly 20 seconds be- 
fore the beginning of a five-minute period ; the notch is also so arranged that the 
contact at s' is again broken at the beginning of that period. In other instances ^ad- 
ditional apparatus is provided, and actuated, through mechanism set in motion by the 
standard clock, whereby strokes indicating the quarters, halves, three-quarters and 
hours, are transmitted over the time circuit. 

The standard clock used for this service in New York City was devised by Mr. 
James Hamblet. 

The clock is located in the Western Union building and is compared each 
day, at noon, with the National Observatory clock in W^ashington, D. C, by means of 
a special circuit set aside for that purpose. 

When a comparison with the National Observatory clock shows a gain or loss in 
the twenty-four hours, if the discrepancy is sufiicient to w^arrant it, the oscillation of 
the pendulum is varied by deftly adding to, or withdrawing from the " bob," a very 

small weight,which,by slightly increasing or decreasing the center of gravitv of the 
pendulum, has the desired effect. 

The standard clock is compared with the clock in Washington, or elsewhere, bv 
means of an electric chronograph, shown in Fig. 270, in which m m' are the electro- 
magnets of double pen registers which are in circuits controlled by the respective clocks. 



358 



AMERICAN TELEGRAPHY. 



A paper tape passes in proximity to the pens in the ordinary way. If the clocks 
are beating seconds, and each is in accord with the other, the dots recorded by the 
pens will be in vertical alignment; if not, one will be in advance of the other. The 
time in advance, in seconds, can be calcnlated to the one-hundredth of a second, or 
less, by knowing the rate at which the paper is running out. If, for example, it 
should be running out at the rate of one inch, per second, and a portion of the paper is 
divided into I GO parts by means of a suitable scale, the space between any two dots 
will indicate the extent of time by which the clocks vary. For instance, in Fig. 
270, the upper row of dots assumedly representing the " Washington " clock and 
that of the lower row the " New York" clock, it is seen by reference to the scale that 
the New York clock is forty hundredths of a second behind the Washington clock. 



ELECTRICALLY SYNCHEOXIZED CLOCKS. 

In addition to the service just described there are many instances in which 
clocks are corrected or synchronized at stated periods by pulsations of electricity 
transmitted by a standard clock. This correction is made by some form of electro- 
mechanical device which, when actuated b}^ the standardizing clock, moves the min- 
ute hand to a given point, either backward or forward, depending on whether the 
clock to be corrected is running slow or fast, that is, within certain limits, as will 
shortly be obvious. 

Bareaud and LUND REGULATOR. — One of the most frequently employed meth- 
ods of synchronizing clocks by electricity is shown in Fig. 271. It is known as the 

Barraud and Lund '* hour regulator." 

FIG. 271. T r • • 

Its Junction is to actuate two arms 
a a, which, in coming together, engage 
with the minute hand of the clock, 
at, or near, XII, and after bringing 
it either forward or backward, as 
may be necessary, exactly to that 
point, immediately release it and 
withdraw out of its path. 

The device consists of the electro- 
magnet M to whose armature a, 
are attached two projections J j'. The 
magnet 31 is in the circuit controlled 
by the standard clock. Opposite 
the ends of the projections j j', the 
two angular arms, or crank levers, a a 
are placed. There is a slot s s' in the upper ann of each lever, into which the ends of the 
projections enter. The armature is so pivoted as to raise the projections j j' up and 
down. The effect of this motion is to cause them to bring together and spread 
apart the lower ends of the lev irs aa. On the lower ends of ^ ^ there are two right 
angular pins p,p', which extend through a curved slot on the top of the dial of the 
clock, as at pp. Fig. 271^, which represents the dial of a clock equipped with this 
correcting device. Normally the pins pp' are at the ends of the slot. Consequently, 




CLOCK SYNCH ROXIZER. 



SYNCHRONIZING CLOCKS. 



359 



as the minute hand approaches XII on the dial, it comes within the 
path of the pins p, p', and if the clock should be either fast or- slow as compared with 
the standard clock, the minute hand will be, at the first second of each hour, placed 
exactly at the hour. 

The correcting apparatus is placed at the top of the clock within the case, as 
"dotted in," in Fig. 271^. The armature of the magnet m is counter balanced by 

FIG 271 a. 




SYNCHRONIZING CLOCK DIAL. 



the weight w. One advantage of this j)eculiar construction of the levers, etc, is a 
large amplification of the motion of the armature at the pins p p' ; and a comparatively 
powerful leverage is also thereby obtained. The minute hands of the clocks to be 
corrected are adjusted so as to be readily moved by the correcting apparatus, wnen 
necessary. 

The hamblet synchronizing apparatus.- -Another clock synchronizing device, 
^ue to Mr. J. Hamblet, shown in Fig. 272, will be readily understood by reference to 
the illustration. 

D is a clock dial, h is a minute hand, d and d' are pins projecting from the 
lower ends of arms a'a; the latter being mounted on the axles of pinions w' and w, 
respectively. The pinions w' and w gear into each other, as shown. The axial 
length of pinion w is greater than that of w'. This permits a toothed segment s to 
gear with a rear portion of w, without coming in contact with w'. The segments 
is part of a lever l which carries the armature a of the magnet m in the synchroniz- 
ing circuit. When the circuit is closed at the hours the lever l and the segment S 



360 



AMERICAN TELEGRAPHY. 



momentarily take tlie position indicaied by the dotted lines. This action of s turns 
the plniou w in one direction, and that pinion, in thus turning, rotates w' in the op- 

FIG. 272, 




HAMBLET SYNCHRONIZING CLOCK. 



Dosite direction. The result is that the arms aa' are brought st arply together, and 
if the minute hand is within their scope it is brought exactly to the hour of twelve, 
as indicated also by dotted lines. The return motion of the lever l restores the arm^ 
to their original positions. 



CHAPTER XXIV. 



HELIOGRAPHY— MILITARY TELEGRAPH SIGNALING, 

Heliogkaphy. 



ETC. 



FIG. 273. 



The term heliography is derived from two Greek^ words — helioy the sun, and 
graph, to write. As ordinarily used, the word signifies a sun picture, or photograph. 
As employed in. telegraphy the term heliography relates to the art of transmitting sig- 
nals by reflections of the rays of the sun, the 
duration of the reflections being made to cor- 
respond to dots and dashes of the Morse or 
any other pre-arranged alphabet or code. The 
heliograph is a device designed to facilitate 
the transmission of such signals. 

Heliography is now quite extensively availed 
of by the military in this and other countries. 
In this country it is employed by the military 
and the meteorological signal service depart- 
ments between outposts where communicatiop 
by wire or otherwise would be difficult and 
in some cases impractic able, if not impossible. 
The average distance apart of such outpost 
stations is about 25 miles. A territory extend- 
ing over 500 miles is covered by this system. 

In Fig. 273 a portable form of heliograph, 
known as MacGregors heliograph, is shown. 
In the figure f is a metal rod, resting on the 
base f', which is itself supported by the legs xx 
X. M is a small mirror, about three inches in 
diameter, attached to the upper end of f by a 
ball and socket joint. The mirror is freely 
movable in the socket. A small, circular portion 
of the mirror is left unsilvered and consequently 
unreflecting, a is an arm, resting also in a ball and socket joint b. A clamping screw r is 
provided, by which the arm may be rigidly held in any position to which it may be 
adjusted. At the upper end of the arm a, a small, adjustable sight vane sv is placed. 
This vane is shown separately, and enlarged, at the left of the figure. 

The instrument is adjusted and used as follows: The sight vane and the mirror 
are set facing the distant station when the sun s is in the direction of that station. The 
operator then looks through the clear glass in the centre of the mirror; and the r- 
shaped notch in the sight vane is placed in line with the distant station. The mirror, 

3^1 




THE HELIOGRAPH. 



362 



AMERICAN TFXEGRAPHY. 



Fig. 274. 



M' 



and the arm carrying the sight vane, are then so adjusted that the hole in the centre 
of the mirror, and the hole in the sight vane, below the v, are in a straight line 
with the distant station. When so adjusted, the dark spot in the reflection, due to the 
clear spot in the glass, is thrown on the bottom of the v of the sight vane. By means 
of this guide the flash is directed on the distant station. Signals may then be trans- 
mitted by simply interposing the hand, or some other opaque substance, between the 
sun and the mirror; or between the sight vane and the mirror. 

When the sun is not towards the distant 
station, the arrangement shown in Fig. 274 is 
used. This consists merely of the addition of an- 
other mirror m', which is placed over the sighs 
vane. A piece of v-shaped paper is placed on 
the face of m. 

The mirror m is now placed towards tlie sun 
s, with its back to the distant station; the second 
mirror m' is placed facing the distant station; 
The rays of s are reflected on m', and, by the 
latter, reflected towards the distant station. The 
operator adjusts the mirrors by looking through 
the hole in the back of m and moving the mirrors 
until he sees the reflection of the distant station 
within the v on m', and, at the same time, the 
dark spot, due to the clear glass on mirror m, on 
the bottom of the v on m'. 

Signals are then transmitted as before. 
It is occasionally necessary to re-adjust this 
instrument to allow for the displacement of the 
reflection caused by the earth's motion. In 
stationary heliographs a clock-work arrange- 
ment, which moves the apparatus automatically 
at a rate corresponding with the earth's motion 
around its axis, is sometimes provided. 
It has been customary to transmit heliographic signals by "flashing " the light on 
the distant station, which was done by turning the mirror towards and away from that 
point. Such signals are now, however, generally transmitted, in military or naval 
operations, by obscuring the ''reflection" by the interposition of some opaque sub- 
stance before the mirrors, the said substance being interposed and removed at suitable 
intervals by means of an electro-mechanical arrangement controlled by an operator. 




THE HELIOGRAPH. 



Military Telegraph Signaling. 

In this country the Morse system of telegraphy was quite extensively employed as 
a field telegraph system during the late civil war, and its efliciency was highly com- 
mended by the Generals in command. 



MILITARY TELEGRAPH SIGNALING. 



363 



The telegraph equipment consisted of Morse relays, sounders and keys, or, fre- 
quently, a pocket relay with key combined; battery and wires, and construction tools. 

For hurried construction, to open np communication with headquarters, reels of 
insulated wire were provided. The battery and the apparatus were generally carried 
in wagons or on pack mules. This method is still practiced in connection with 
military operations in this country. 

Flag signaling, termed " wigAvagging,'' and flash signaling have long been em- 
ployed in military operations by all the European war departments, and by the war 
department of this country, where the electric telegraph is not available. Torches 
at night take the place of the flag, and lanterns the place of the heliograph. 

In flag and torch signaling as well as in heliographic and lantern signaling the 
American Morse Code (page 57) is nsed by the United States war department, when 
a dot and dash alphabet is to be availed of. The United States Army and Navy 
Code, known as the Myer Wigwag Alphabet, and extracts from official instructions 
regarding same, and also for the use of the Morse code in wigwagging, etc., are given 
below. 



U. S. Akmy axd Navy Signal Code. (Myee Wigwag Alphabet.) 

Y.. 
Z.. 

I . o 



A 22 

B ... .2112 

C 121 

D ,, . . .222 
E......12 

F 2221 



H... 

I..,. 

J... 

K. o , . 2121 

L. . . , ,221 



221 1 
. 122 
... I 
1 122 



M. ... 122 1 

No II 

0. .. ...21 

P = . . .1212 
Q, . o . 121 1 

R.,.».2II 



S.....212 

T 2 

U 112 

V . . . .1222 

W\. o .1121 

X . . . .2122 



2 . „ 

3 »^ 

4 .0 



. . Ill 

. 2222 
. mi 

. 2222 
.1112 

o222I 



5 •• 

6 .. 

7 . . 



9 .. 
o . . 



. . 1122 
o . 2211 
. .1222 
.'. 21 1 1 
. . 1221 
. .2112 



Abbreviation's. 



a. . . .after, h, . . .have. t. , . .the. 
b. . . .before, n. . . aiot. n. . . .you. 
c...cCan. r. . . .are. nr. , . .your. 

End of a word ........... ........ 3 

End of a sentence ;^;^ 

End of a message ;^^;^ 

Aye " I understand". 22, 22, 3 

Cease signaling 22, 22, 22, ^^^ 



Wo... word. X X 3 . . " numerals follow " 
wi. . . .with. or '*^ numerals end.'" 

y . . . . why. sig. 3 . . signature. > 

Eepeat last word. .........121, 121, 3 

Eepeat last message ...121,121,121,3 
Error. .....................12,12,3; 

Move to the right .........211, 211, 3 

Move to left. ...........0.221, 221, j 



Code Calls. 



A. S. U. Action Signals Use. 

I. C. U. International Code Use. 

T. D. U. Telegraph Dictionary Use. 

Gr. S. U. General Signals Use. 

C. A, U. Cipher ''A" Use. 



C. B. U. Cipher ^'B" Use, etc. 

G. L. U. Geographical List Use. 

N. L. U. Navy List Use. 

V. N. U. Vessels' Numbers Use, 



Ii^STRUCTioi^s for signaling with flag, torch,, hand-lantern, or beam of search 
light, by the Myer and Morse codes. 



3^4 



AMERICAN TELEGRAPHY. 



The motion " i '' to the right corresponds to that of the Morse "dot" in the 
following instrnctioDs; the motion " 2" to the left, to that of the Morse "dasli^^; 
the motion to "front," to that of the Morse "space." 

Thus right (i), left (2), right (i), represents the letter c — that is "121/^ etc. 
Otherwise the instructions apply to both codes. For fog signals or fog horns, how- 
ever, one (i) toot, about one-half second, will be "one" or " i ", of the Myer 
alphabet. Two (2) toots in quick succession will be "two" or "2", and a blast 
about two. seconds long will be "three" or " 3". The ear and not the watch is to 
be relied upon for the intervals. 

For signaUng with flash lantern, heliograph or search-light shutter, same as in 
fog signals; substitute "short flash" for "toot", and "long steady flash" for 
"blast." The elements of a letter should be slightly longer, 

TO SIGNAL WITH FLAG OR TQROH. 

The flagman faces exactly toward the communicating station; staff is vertical in 
front of centre of body, but at height of waist. Fig's. 276, 277. The dot ( - ) is rep- 



FIG- 276. 



FIG. 277- 






WIG-WAGGING. 

resented by a motion to the right, and the dash (— ) by a motion to the left of the 
Bender The i;^^^^, whether separating elements of spaced characters (C. O. R. Y. Z. 
and " &.") or separating words, will be represented by a "front" motion. Fig. 278. 
Thus the motions : 

Right right, front, right, represent C. 

Right, front, right, represent O. 

Right, front, right, right, represent R. 

Right, right, front, right, right, represent Y. 



MILITARY TELEGRAPHY. 



65 



FIG. 279. 



Right, right, right, front, right, represent Z. 
Right, front, right, right, right, represent &. 

Each motion will embrace an arc of 90°, starting from and returning to the 
vertical. 

The /o?ig dash (letter " L " and numeral " naught ") is distinguished from the " T " 
dasli by a slight pause at the lowest point of dip, and with this exception there will be 
no pause whatever between the motions required for any single letter. 

A slight pause will be made between letters. 

At the end of each word, abbreviation, or conventional signal the space signal, or 
*• I'ront '' motion, is made, preceded and followed by a pause equivalent to that made be- 
tween letters. 

CONVENTIONAL SIGNALS FOR FLAG OR TORCH. 

To call a station. — Signal the '' call letter" of the station required, or, if the call 
letter be not known, signal " A " without pause until acknowledged. The calling sta- 
tion will then proceed with the message. 

To acknowledge a call. — Signal " I " 
three times followed by "front " and the 
call letter of the acknowledging station- 

To break or stop the signals from the 
sending station. — Signal " A " without 
pause until acknowledged. Fig. 279. 

To start the sending station after 
breaking. — Signal "G A" followed by 
"front " and the last word correctly re- 
ceived: the sender will immediately 
resume his message, beginning with the 
word indicated by the receiver. If noth- 
ing has been received signal "R R," the 
sender will then repeat all. 

Error in sending. — Signal seven dots 

( ) rapidly followed by "front," 

and resume the message, beginning with 
the last word correctly sent. 

End of address. — Signal the period 
( -) followed by " front.'' 

Signature follows. — • Signal " sig " 
followed by "front.'' 

To acknowledge receipt of a message. — Signal " O K " followed by " front " and per- 
sonal signal or initial of receiver. 

CONVENTIONAL SIGNALS FOR HELIOGRAPH OR FLASH LANTERN. 

To call a station. — Turn a steady flash on the station and keep it there until an- 
swered by a steady flash. Both stations will then adjust each on the other's flash- 
When adjustments are satisfactory, tlie station called will acknowledge :ind cut oflF its 
flash, and the calling station will proceed with the message. 




WIG-WAGGING. 



366 AMERICAN TELEGRAPHY. 

To acknowledge a call . — Signal " I " three times, followed by the call letter of tne 
acknowledging station. 

To break or stop the signals fro??i the scfiding station. — Signal " A " without pause 
until answered by a steady flash 

7o start the sending station after breaking. — Signal " G A " followed by the last 
word correctly received ; the sender will immediately resume liis message, beginning 
with the word indicated by the receiver. If nothing has been received signal " K R," 
the sender will then repeat all. 

Error in sendi7ig.— '^\<g\\'i\\. seven dots ( -) rapidly, and resume the message, 

beginning with the last word correctly sent. 

Adjustment. — If the receiver sees that the sender's mirrors needs adjusting, he will 
turn on a steady flash until answered by a steady flash. When adjustment is satisfac- 
tory, the receiver will acknowledge, and the sender will resume his message. 

End of address. — Signal the period ( -). 

Signature follows. — Signal " Sig. " 

To acknowledge receipt of a message. — Signal "OK" followed by personal signal 
or initial of receiver. 

CONVENTIONAL SIGNALS FOR TELEGRAPH. 

To call a station— '^xo^wA the " call letter" of the station required until acknowl- 
edged, signing at intervals the " call letter " of the station calling. 

To acknowledge a call. — Signal " I " three times followed by " call letter " of ac- 
knowledging station. 

To break or stop the signals from the sending station. — Open the key. 

To start the sending station after breaking. — Signal '' G A " followed by the last 
word correctly received ; the sender will immediately resume his message, beginning 
with the word indicated by the receiver. If nothing has been received signal " R R," 
the sender will then repeat all. 

Error in sending— Signal seven dots (- * - -) rapidly and resume the messaare, 

beginning with tlie last word correctly sent. 

End of address. — Signal the period ( -). 

Signature follows. — Signal " Sig."' 

To acknowledge receipt of ?nes sage. — Signal " O K," followed by personal signal or 
initial of rpceiver. 

MESSAGES BY FLAG, HELIOGRAPH, TELEGRAPH, ETC. 

The following will be the order of transmitting the several parts of a menage: 
ist, number of message and " call letter" of sending station; 2d, operator's personal 
signal; 3d, the check; 4th, place from and date; 5th, address in full; 6th, period (ad- 
dress complete); 7th, body of message; 8th, Sig. (signature follows) ; 9th, signature. 

Abbreviations should not be used in the body of a message, and numbers occur- 
ring therein must be spelled out in full. 

It may be added that the foregoing conventional signals, for flag and torch sig- 
naling, are practically similar to those employed in commercial telegraphy in the 
(Juited States and Canada. 



UNITED STATES SIGNAL CORPS STATION KIT. 366^ 

The United States Signal Corps Statiox Kit, 

The connections of this '^kit/' or combined telegraph, telephone, and "buzzer" 
outfit, are shown in Fig. 279^^ The kit comprises a buzzer M, the telephone receiver 
R and transmitter t, the key k for Morse and buzzer sending, the necessary switches 
A, B, c, D, for changing from one to another method of communication, and a battery 
of about 8 dry cells b'. The whole is contained in a 'lox about nine inches square 
and nine inches deep. It is opened into two equal parts when in use. The telephone 
receiver is used for receiving the ^lorse and buzzer signals and for speech. When used 
for open-circuit Morse or double-current working, the sounds are heard in the receiver 
as clicks, corresponding to the sounds of the Morse sounder, the click at the closing 
being louder than that at opening the key K, as will be explained. When used for 
buzzer working the signals are received in the telephone receiver as a succession of 
pulsations which produce a buzz or tone that is broken up into dots and dashes, that 
is, short and long tones. 'J'he telephone system has the usual primary and secondary 
induction coils i. For the operation of the transmitter t only half of the battery B 
is used, as the full battery would perhaps })roduce "frying" in the transmitter that 
would impede speech. 'J'he buzzer M is the same in principle as that described on 
page 256, but its general construction is quite dilfei'ent. Its coils, of 10 ohms each, 
are connected in multiple to give sharper action. Its armature-lever or circuit- 
breaker e is of steel, and requires careful adjustment for best results. The contact r 
is mounted on a spiral spring cairied on an adjustment-sci'ew a\ the armatuie- 
lever is also supplied with an adjustment- screw ^, all strongly made. The key K 
is of special construction. In the drawing its under-contacts are projected in order 
to show the connections more readily. The key has one back contact and two front 
contacts. 'J'his outfit is used for station work as distinguished from the field outfit. 

To simplify the ensuing explanation the buzzer arrangement may be considered 
as analogous to the Varley-Athearn device, and the Morse arrangement to that of the 
phonoplex described in Chapter XXII. 

Buzzer Working. — Switches a, c, d are turned to the left, b to the right, for 
buzzer working. (It will simplify the study of these devices if the reader will 
draw, with a pencil, lines on the diagram to indicate the different positions of the 
switches.) When key k is closed a metallic circuit is foi-med as follows: From 
positive pole of battery b to post 11, to post 10, to switch c, to contact ^, to key- 
lever, to trunnion q^ to post 9, to the coils of M at'<:^, through coils to armature-lever 
€, to back contact r, to posts 8, 12, and negative pole of battery. At this time it 
will be understood the buzzer is active and is sending out rapid pulsations to line by 
way of post 9, trunnion </, key-lever to contact n, to post 14, to posts 4 and 2; and 
to earth e by way of armature-lever e and post i, which pulsations are heard as long 
and short tones in the distant telephone. When, on the other hand, key K is open 
the battery metallic circuit first traced is open at contact t and consequently no 
pulsations are developed at m. When key k is closed the receiver r is short-circuited, 
as may be seen, by way of posts 4, 14, trunnion (7, post 9, switch b, and post 5. 

For receiving buzzer signals key k is kept open, and the telephone receiver is 
then in the circuit from line, to post 2, to post 4, through receiver, to post 5, to top 
of switch B, to and through coils m, to post i, to earth e. 



366^ 



AMERICAN TELEGRAPHY. 



Morse Workij^'G. — Switches a, b, c, d are turned to the right. With switch 
A to the right, circuit-breaker e oi M is short-circuited and therefore cannot act as a 
buzzer. Tliere is then, when key k is open, a metallic .circuit from the positive pole 
of b', to post II, to switch d, to back contact i of k, to trunnion q^ to post 9, to 
and through coils of m, to lever e, to r, and back by way of posts 8 and 1 2 to 
negative pole of battery. With K closed the metallic circuit is from the positive 
pole of b' to posts II, 10, to switch c, to and through a resistance coil of 10 ohms, 
to contact ^, to key-lever, to trunnion ^, post 9, to and through coils of M, its 
armature e, and back by way of r, posts 8 and 12, to negative pole of battery. When, 




FIG. 279<^. 

therefore, the key is open or closed in buzzer sending the magnet m is charged by 
battery b'. When the key is in transit from open to closed, and vice versa, coils M 
discharge into the line by way of switch b, post 5, receiver r, and posts 4 and 2; 
and to earth e by way of post i. The difference in the sound of the Morse characters 
is obtained by the use of the resistance at switch c. As this resistance is not in the 
metallic circuit of M when key K is open, but is in that circuit when k is closed, the 
sound is louder when the key starts to close (that is, when the circuit is- broken at 
back contact i), and weaker when the key starts to open, thu^ giving the equivalent 
of the front-and-back stroke of the Morse sounder. 

Telephone Workit^g. — Switch a may be open or closed; b is turned to the 
left; c may be on either contact; and D is open. The transmitter circuit may be 



FIELD KIT OF UNITED STATES SIGNAL CORPS. 



366^ 



traced from the middle of battery b' to post 13, to and through primary p of induc- 
tion coil I, to post 7, through transmitter t to post 6, to posts 8, 12, and negative 
joole of battery. The route of the received telephonic signals is from line, to post 2, 
to and through receiver r, to switch b, to secondary coil s, to post i and earth e. 

When the buzzer or telephone system is superposed upon a regular Morse 
telegraph circuit the line wire is connected to post 3, which interposes the condenser 
c', through which of course the pulsatory and telephone currents pass unobstructedly 
as explained, page 347. Otherwise the connections remain the same as just noted. 



IS 




^ 



I 



Field Kit of United States Signal Coeps. 

Anotner arrangement of the U. S. signal corps bazzer and telephone circuits 
shown in Fig. 279^. In this, for the sake of clearness, the switches are 

omitted. AVhen set for 
buzzer signals the opera- 
tion is as already de- 
scribed. When arranged 
for telephoning the cir- 
cuit-breaker e r is short- 
circuited. No secondary 
coil is used in this case, 
the impulses in the coils 
of M caused by the varia- 
tions of the resistance in 
the telephone transmitter 
(due to the voice) suf- 
ficing. 'J'he condenser c' 
is employed for the pur- 
pose already mentioned. 
The transmitter is con- 
nected to posts 6 and 7 ; 
the receiver to posts 4 and 
5 ; the other connections 
are as marked. The field 
kit weighs about 5 lbs. 
and is about half the size 
and weight of the station 
kit. The field kit is not 
used for Morse working. 
As the batterv in use 




ih 



m 



FIG. 2'J()d. 



on this apparatus is of the open-circuit tvpe, switch D should always be kept open 
when the apparatus is idle. 'Jlie switches should always be set for Morse or buzzer 
working when not being used for telephone working. When it is desired to use a 
regular Morse system and the buzzer on the same line simultaneously, the buzzer 
apparatus is connected outside of the Morse appai'atus virtually as in the case of 
simultaneous telegraphy and telephony, E f, Fig. 261. 



366^ 



AMERICAN TELEGRAPHY. 



In actual operations in the field, these and more or less similar outfits have 
been found of great utility in various countries, the lightness and compactness of the 
apparatus being a great advantage. The Morse method can be used over compara- 
tively short distances; the buzzer for longer distances, and especially when the 
insulation of the line is low. On many occasions the buzzer method has been 
successfully used with the bare wire lying on fences, trees, and even in water. The 
Morse and buzzer methods are generally preferred for accuracy in the case or 
important correspondence. In some European military departments, however, a 
recording apparatus is preferred. 

The foregoing description of these kit systems is based on data kindly supplied 
by Gen. A. W. Greely, Chief Signal Officer U. S. Army, and Capt. E. Russell. 



CHAPTER XXV. 



The American District Telegraph Messenger Servick 



FIG. iSo. 



This "service " relates to the supplying of messengers, policemen, firemen, etc., 
at the call of the " subscribers " in whose houses or offices an instrument termed a 
**call box " has been placed. 

This call box, which is shown virtually as it appears in practice, in Fig. 280, 

is electrically connected with a central office, at 
which the messengers, policemen, firemen, etc., are 
located. Each box is «u])plied with '' make and 
break'' attachments which are set in motion by the 
turning of a crank on the cover of the box, and 
which attachments, when thus operated, transmit to 
the central office a specified number, which indi- 
cates to that office the location of the signaling box. 
The electrical connections for this service, which 
are quite simple are outlined in Fig. 281. Inthefigure 
R is an ordinary Morse relay, wound to about 100 
ohms. B is a single stroke electric bell, whose elec- 
tro-magnet is wound to about 4 ohms ; g is a single 
or double pen Morse register, the magnet of which 
is also wound to about 4 ohms, b and g are in the 
one local circuit, which, it will be seen, is controlled 
by the armature lever of the relay k; the contact 
point of the latter being on the back stop. lc is 
a local battery of 4 to 8 Leclanche cells. c' is the 
call- box- circuit battery, of 1 2 or more gravity cells, 
according to the length of the circuit, s is a switch 
used for testing and changing circuits, and is shown 
and described more fully further on. All of those instruments and batteries are located 
in the central office. 

Call boxes. — At the right of Fig. 281, cb represents the circuit- breaking arrange- 
ments and crank of a call box in a subscriber's office. The crank c is mounted, 
with a recoil spring, on a shaft, as indicated. A cog-wheel, cw, is also mounted, loose- 
ly, on the crank shaft. A " break- wheel " w is geared with the cog-wheel cw in such 
a manner that it receives a tendency to turn in the direction shown by the arrow, 
but it is normally prevented from turning by the engagement of the pin/ on its side 
with the curved cam k attached to the prolongation of the crank arm. A\Tien how- 
ever the crank lever c is pulled to the right, preparatory to sending in a call, the cam 
is moved out of the path of the pin/, and the wheel w is then free to move. By a 

367 




DISTRICT SERVICE CALL BOX' 



368 



AMERICAN TELEGRAPHY. 



suitably arranged pawl and ratchet the cog-wheel cw is prevented from moving 
when the crank is pulled down. (A practically similar pawl and ratchet is shown ia 
Fig. 282.) The effect of turning the crank shaft is to wind the recoil spring. When 
the crank is let go the spring unwinds and as it does so the wheel w begins and com- 
pletes a revolution and the crank lever returns to its normal place. When the latter 
has done so the camK is again in the path of pin p; hence the wheel w is stopped in 
its normal position. 

The contact spring a is supported by the frame of the box, but is insulated 
therefrom, formally, one end of a rests on the periphery of the break-wheel w, 
thus keeping the circuit closed. The periphery of the break-wheel is notched practi- 
cally as shown in the figure, so that, as the wheel is revolved, the spring a alternate- 



o. ^ 



Xc 



B 

CO 



h 



B 



ililili|iiiiiiiiiiiy 







CENTRAL OFFICE AND CALL BOX— DISTRICT MESSENGER TELEGRAPH. ! 

j 

ly passes over the metal periphery and falls into the spaces between the ''teeth," there- 
by opening and closing the circuit. In the figure, there are 3 notches a uniform dis- 
tance apart, further on another notch In turning once, therefore, the wheel will first 
break the circuit thrice, in comparatively rapid succession, and, after a longer pause, 
will again break it once. This will, of course, operate the electric bell and the 
register, in the central office, which instruments will, i*espectively, ring and record the 
number of the signaling box ; in this case 3 1 . 

Although but one call box is shown in Fig. 281, it is plain that a large number 
of such boxes may be placed in one circuit. In practice it is not uncommon to have 
fifty or more call boxes on one circuit, but the maximum is about one hundred, it hav- 
ing been found that more than this number too largely increases the chances of sig- 
nals clashing. 

In order to guard against the opening of the circuit in any of the call boxes 
when the instrument is in its normal position, by a failm-e of the contact spring a 
to make perfect contact with the periphery of the break-wheel, a short circuit 



CALL BOXES. 



369 



FIG. 282. 



is provided which is only complete when the cam k rests against the contact/', whicli 
it normally does, but from which it separates when the crank lever is pulled, as will 
be obvious on examination, thereby leaving the circuit free for the operation of the 
break-wheel. The contact strip/' is suitably supported in the box on the insulated 
piece d. 

Another form of " break- wheel " used in the district messenger service is shown 
in Fig. 282. In that figure k is the crank shaft. The crank lever is not shown. A 
coil spring s is attached at one of its ends to the crank shaft; its other end is rigidly 
attached to a rod f fastened to the framework of the box. The shaft k carries a 
wheel V, (indicated by the dark strokes) on the periphery of which are two detents 
D, d' opposite each other, w is a large flat wheel, loosely mounted on shaft k. The 
pawl, or "click" e, carried by the wheel w, is pressed against the periphery of v by 
the tension spring p. AVhen the crank is turned to the right, a full turn, the coiled 
spring s is wound up more tightly, and, at the same time, the pawl r drops in be- 
hind the detent d. As a result the coiled 
spring, in unwinding, revolves the crank 
shaft and wheel v, and, since the pawl R is 
then caught by detent d, the large wheel 
w is also revolved in the direction of the 
arrow, and the contact, or " trailer " c, al- 
ternately resting on the brass of the wheel 
w and suspended, as in Fig. 282, over the 
^'^WT open spaces in that wheel (thereby opening 
and closing the circuit), sends in the regu- 
lar number of the box. Owing to the size 
of wlieel w there is room to cut the num- 
ber of the box out twice, as in the figure, 
so that, if the crank is pulled a prescribed 
maximum distance, the number will be Lent 
in twice, thereby indicating a special sig- 
nal. If pulled a less distance the number will be sent in but once. The movement 
of wheel w is always in the same direction. 

The function of the small toothed wheel t, which is geared with the large wheel 
w, and the escapement e, is to regulate the speed of uncoiling of spring s. The coiled 
spring is prevented from running completely down by the extension b, attached to 
(Shaft K, which, at a suitable point engages with a check pin attached to the frame- 
work of the box. 

For other examples of the " District" call boxes, see the "Fix" combination "call'* 
and burglar alarm box. 

RETURN SIGNAL CALL BOXES. 

In the district service system described, it may have been noticed that there is 
nothing to tell the subscriber whether or not his " call " has been received in the cen- 
tral' office. Perhaps it may be truly said that the average user of the call boxes 
does not care to know; preferring to have visual evidence of the fact that the call 




BREAK WHEEL. 



has been received, in the prompt appearance of the messenger, 



370 



AMERICAN TELEGRAPHY. 



But to meet the wishes of such as desire to have an immediate acknowledgement, 
from the central office, of the receipt of the call, various, so-called, " return " signals, 
to be actuated, automatically, or by the clerks in that office, have been devised, and, 
in some instances, put into service, one of which, the Van Size return signal box, will 
now be described. 

THE VAN SIZE EETURx siGXAL Eox. — " Rctum " siguals are, generally speaking, 
either audible or visual. The Van Size return signal box gives an audible signal. 
This device and the necessary attachments for its operation are shown in Fig. 283. 

FIG. 283. 




CONNECTIONS — VAN SIZE RETURN SIGNAL. 

The mechanical and electrical portions of this box are nearly identical with the 
ordinary call box. 1 he bell b, relay R, register g, etc., at the left of figure are as- 
sumed to be in a central office, co. The return signal apparatus proper is placed in 
the bottom of the call box c t5. 

It consists of a small electro-magnet m, whose armature, when actuated by a cur- 
rent -flowing in the magnet, taps a bell. 

The operation of the return signal is as follows : In the first place the mechanism 
of the box is so arranged that every movement of the crank c causes the break- wheel 
w to make two revolutions. During the fii'st revolution tlie number of the call box 
is sent in as usual. During the progress of the second revolution the thicker portion 
of the curved cam K impinges against the contact spring s, causing it, as in the figure, 
to press against the lower contact spring s'. These two springs are normally separ- 



DISTRICT TELEGRAPH. 37I 

ated. When the cam passes the spring s, the latter resumes its usual position. A 
wire connects s, via the bell magnet m, with the earth. Another wire connects s' with 
a screw post in the box, to which is also connected one side of the main circuit, as 
indicated in the figure. At the central office, b is a "strap" key, which, when de- 
pressed, first opens the main line circuit at x, and next, puts a special battery c' to a 
portion of the main line circuit. It is then obvious that when key b is depressed at 
the time the cam k has brought the two springs s and s' together, in the call box, that 
there is a circuit from the ground in the central ofiice to the ground at the call box, 
via the bell magnet m, and the latter will ring. 

Hence, in order to send the return signal, it is only necessary that the attendant 
at the central office, when he hears the first signal of the box, should depress the but- 
ton B and hold it depressed for a few moments, or until the cam k temporarily closes 
the circuit, tliereby ringing tlie bell in the call box, which is evidence to the subscriber 
that his call has been received. 

The successful operation of this return signal depends upon the promptness of 
the attendant at the central office, for, should he fail to depress the button while the 
cam is passing the circuit-closing contact springs, no return signal can be sent back 
until the subscriber repeats his call. 

Another audible return signaling device will be shown in connection with the 
" Field and Firman " call box. , 

Visual return signal devices, as the name implies, consist of means, more or less 
analogous to the foregoing, whereby an electro-magnet in the call box brings into 
view some pre-arranged letter or character at an opening in the box. 

Neitlier audible nor visual return signals are used very extensively in the district 
messenger service, but their use is increasing. It may be added that at one time an 
electro-magnetic arrangement was attached to the call boxes wliich permitted the 
customer to ascertain for himself, by depressing a button and llistening, whether the 
line was being used by others. This was, however, to avoid clashing, of signals. 

When, as occasionally happens, two subscribers pull their call boxes simultan- 
eously the signals are, of course, jumbled. There is at present no remedy for this but 
to wait until the subscribers call again, unless the central office clerk is able to sep- 
arate the signals, which, from experience, he may be able to do. It is said, and miy 
be noted in passing, that almost every call box has a characteristic of one kind or 
another in the manner of transmitting its signal, with which the central office clerk 
quickly becomes familiar, and this characteristic is frequently sufficient to enable 
him to determine from which box a call has emanated, even before it is completed. 
For instance, suppose a box to have the number 234. Perhaps before 2, 3, is signaled 
the "characteristic" will have identified the box so calling. This feature is occasion- 
ally of utility in enabling the clerk to distinguish a call when the entire signal may 
have been prevented from coming in by the cause just mentioned, or others, such 
as the crossing of the wire, etc. 

District service magnet bell.— This instrument is shown as b in Fig. 2^^,. 
It is an ordinary electric bell; the clapper being, by suitable means, attached to the 
armature of its electro-magnet. When the relay r is operated by a call box the clap- 
per strikes the gong a number of times corresponding to the number of the box. The 



3/2 AMERICAN TELEGRAPHY. 

object in using these bells, in addition to the double-pen register, is to guard against 
failure of the register to record, and also as an indict- tion of the "arrival" of a 
call. As a matter of fact the " oall " is more frequently taken from the bell than 

VIG. 284. 



DOUBLE PEN REGISTER. 



from the number embossed on the paper strip of the register, and the latter becomes, 
m time, more a means of securing a record of calls received, than otherwise. In some 
central offices the bell also is dispensed with, the clerk relying on the sound of the 
register to attract his attention to a call. 

Double pen register. — One of the forms of register u&ed in the district mes- 
senger service for recording "calls," automatically, is illustrated in Fig. 285. This 
is known as a self -starting, " double-pen '' register. The action of this register is very 
simple. A reel carries paper tape which is passed between two rollers, as shown. 
These rollers are given a constant tendency to rotation by clock-work within the box- 
There are two magnets within the box, each magnet in a separate circuit. The arma- 



SELF-STARTING REOfSTERS. 



373 



FIG. 285. 




SELF-STARTING REGISTER — THEORY, 



FIG, 286. 



ture level's of these magnets are extended to a point directly under the paper tape; 

each lever carrying a stylus (seen in side view in Fig. 285, at x.) When either of the 

magnets is operated the clock-work is started; {in a manner presently to be explained} 

the paper is also started, and the stylus 
indents the paper as many times as ihe 
circuit is broken, and with intervals ' cor- 
responding to those of the number of 
the box from which the call comes. 

By the placing of two magnets and two 
pens in one frame the clock-work for one 
register is saved. 

Self-stakting registers. — There are 
several kinds of self-starting registers in 
vogue. One such, which is in quite 
general use, is theoretically shown in 

Fig. 285. Only one magnet and one pen, or stylus, is shown. 

D is the drum containing the spring which drives the clock-work, e is the wheel 

most remote from the drum; it is connected with the 

clock-work by gearing, omitted in tl)e figure. The 

shaft A of wheel e carries an arm p', as shown, l 

is a lever trunnioned at t. f is an extension from 

that lever. This extension rests easily against 

the flat end of the drum d. Consequently, as the 

drum revolves it tends ^to raise, by friction, the 

extension r.. This action, when continued long 

enough, brings the left end of the lever l into a 

position where it engages with the extended arm 

p' of A. This at once stops the rotation of the wheel 

E and, therewith, the entire clock-work. 

The armature lever of magnet M is provided 

with a horizontal extension, or arm, is'. This arm, 

when the armature of m is attracted, pushes forward 

the extension F, thereby removing the left end of 

lever l from the path of the rotating arm p, which 

at once releases the clock-work. It will be under- 
stood that as long as signals follow each other in 

quick succession the extension, n, will continue to 

strike against f, thereby keeping lever l out of the 

path of the arm p'. The action of the drum in moving 

the extension f is so regulated that, when the signals cease, but a few inches of paper 

run out before the clock-work is stopped. 




MULTIPLE CALL BOX. 



" MULTIPLE CALL BOXES. 

When it is desired to furnish a subscriber witli more than simple messenger ser- 



374' 



AMERICAN TELEGRAPHY. 



FIG. 287. 




vice, for instance, fire alarm, burglar alarm, calls for doctor, etc., a pre-arrangement 
may be made whereby, for example, the number of the call box once sent in, may 
signify that a watchman or messenger is wanted; twice sent in, police assistance; 
thrice sent in, a fireman; four times, a doctor, or other special want. Thus, in the latter 
case, the subscriber would be required to turn the crank of the box four times, 
consecutively. 

But to avoid this trouble, and to avoid confusion due to errors in counting turns, 
a " special " or " multiple " call box is frequently provided, which may be set by the 
subscriber at a point signifying a call for messenger, police or physician, and one 
turn, or partial turn, of the crank 
then suffices to send in the de- 
sired signal, automatically. 

One box of this kind resembles 
the ordinary single call box, save 
that it is furnished with 4 pawls, 
or clicks, by means of which, 
when the crank is turned beyond 
one, two, three or four of the 
pawls, the break-wheel is caused 
to make a corresponding num- 
ber of revolutions, thereby send- 
ing in its number as many times 
as the wheel revolves. On the 
cover of such boxes the point to 
which the crank should be 
turned to secure the service de- 
sired is plainly marked, as shown 
in Fig. 286. The detent d 
on the cove;i" of the box, prevents 
the crank from passing the mes- 
senger, or watchman, call, until 
it, the detent, is moved out of 
the way. 

THE FIELD AND FIRMAN ELECTKIC CALL BOX. 

The form of "multiple call" and '' return signal" box illustrated in Fig. 287, is 
employed in district messenger service. It is also used, in slightly modified forms, in 
some police telegraph systems, as a means of transmitting special signals from patrol 
boxes, {see Gamewell Police Patrol Telegraph.) 

The theory of this box is outlined in Fig. 288. k is the crank lever; bvv is a 
break-wheel which transmits the ordinary box number, sw is a wheel used for 
transmitting special signals, in a manner to be described shortly. This wheel may be 
moved to the left by the pointer p; both being on the same shaft. A segment of 
a wheel, with cogs gg, is rigidly attached to the side of bw. A similar segment 
with similar cogs g'g^ is attached to the side of pw. The shaft of break-wheel bw h 
geared with the wheel w, which latter is mounted on the winding shaft s. Wheel sw 



PLACE THE 

/ POINTER ON THE SERVICE^ 

REQUIRED BEFORE PULLING 
DOWN THE STARTER 



IF THE 
RETURN 5ICNALISN0T HCARD 
V WITHIN TEN SECONDS > 
V REPEAT THE CALL. . ^'' 



^ 



FIELD AND FIRMAN CALL BOX. 



MULTIPLE CALL BOXES. 



375 



FIG. 288. 



is no^ normally geared with any of the other wheels. A curved arm c on shaft s 
acts as a stop for the wheel bw by engagement with the pin t. When the crank 
lever K is pulled down, c is moved out of the path of the pin. This permits the 
wheel BW to make one revolution before the- crank lever shaft s, in the process of un- 
winding, places c again in the path of pin ^. 

By means of a ])awl and rat- 
chet, not seen in the figure, the 
wheel Bw, which is loosely 
mounted on its sliaft, is rotated 
in one direction only, and does 
not move when the crank lever 
is being pulled down in the act 
of winding the recoil spring; 
in which respect it resembles the 
break-wheel of the ordinary call 
box described. 

A rod, or lever, l, pivoted at 
.r, carries a roller r on its upper 
end. When sw is rotated the 
roller r rides in and out of teeth 
k on the periphery of sw. -As 
it does so the contact between 
the points /i li at the lower end 
of L is broken. Ordinarily 
the contacts //, h' are short-cir- 
cuited by the dotted wires and 
contact spring /. It will be 
seen, however, that as soon as 
break- wheel Bwbegins to revolve 
this short-circuit does not exist, 
as at that moment the spring / 

FIELD AND FIRMAN CALL BOX,THEORY. SeparatCS frOm thc piu /. 

In the present position of the wheels bw and sw, it will be seen that bw may ro- 
tate continuously without any opportunity being given for the cogs gg on bw to 
engage with cogs g'g' on sw. When, however, the pointer p, controlling sw, is 
moved to the left, it brings, depending on how far to the left it is moved, one or more 
of the cogs g' into the patli of the cogs g, with the result that, as the wheel 
BW rotates, the cogs g engage with the cogs g' and cause the wheel sw to resume its 
former position. 

When, therefore, it is only desired to send an ordinary service call, the pointer 
p is not moved, and the pulling of the crank lever k simply effects the turning in of 
the box number by the medium of the spring contact f and the breaks v v on the 
break-wheel. When it is desired to send in a special signal, the pointer is moved over 
to the place, or "stop " corresponding to the desired service. For instance, if it is 
placed over " coupe," the lever will ride over tw^o teeth k, as it does so opening the 




37^ AMERICAN TELEGRAPHY. 

contacts at h h,' twice, but as those contacts are still short-circuited via/ and /', the 
circuit is not affected. The pointer having been thus "set", the crank lever is operat- 
ed, whereupon the break- wheel bw proceeds to make its revolution. In so doing it 
first sends in the box number by opening and closing the circuit between the spring 
F and wheel bw. This done, the spring contact p then rests steadily on the peri- 
phery of BW. The next moment the cogs g on bw engage with g', moving sw back 
into its former position, which causes the roller r to ride back over two teeth k^ 
thereby, (the short-circuit Vrn^ff now being broken) opening the main circuit twice at 
h h'. The signal, as thus sent, is recorded by the register or bell at the central office ; 
the signals following the box number indicating the nature of the service. 

A " return signal " arrangement, by means of which the subscriber may know 
that his call or signal has been received, is provided in the box. . Its operation is as 
follows: The lever A, from which the ''tapper" of bell v, is extended, is normally 
held by the spring J- in the position shown in the diagram; the armature lever of 
magnet m resting against one of the ends of a, as shown. This magnet is ordinarily 
short-circuited, as shown at the contact point c, which latter is insulated from the 
frame- work of the box. When the crank lever k is pulled down, the arm ay 
which moves with that crank, turns the lever a on its trunnion, opening the short- 
circuit at c and placing the catch ^ at a point where it is engaged by the detent d on 
the end of the armature lever, whereby the lever a is held in that position even after 
the arm a has been restored to its usual position. The spring s' is of sufficient ten- 
sion to hold the armature lever away from the magnet against the attraction of the 
core occasioned by the current due to the main battery in the central office. When, 
however, the attendant in that office hears the signal just sent in, he depresses a 
key, which action adds another battery, momentarily, to the circuit. The increased 
current has the effect of attracting the armature of m, thereby releasing the lever a, 
which quickly resumes its normal position, and, as it does so, the tapper strikes its 
bell B once, thus announcing the receipt of the signal or call ; at the same time 
the magnet m is again ctit out of the main circuit by the short-circuit via c. 

The number of cogs g g'. on the segments attached to bw and sw, may, of course, 
be increased to correspond with any number of different, " special" signals, desired. 

DISTRICT SERVICE SWITCHES. 

As a rule metallic circuits are used in the district messenger service, inainly be- 
cause such metallic circuits are not affected by one accidental *' grounding '' of the 
circuit, as would be a " ground return " circuit. 

In order that one such accidental " ground " may not remain long unnoticed, it 
is customary to test each district circuit every hour, by grounding it at the central 
office, when, if any other portion of the circuit be grounded, a "test" instrument, 
placed in the "ground" wire in the central office, will ring; the circuit of the test in- 
strument being thereby completed. To facilitate testing and switching of circuits each 
central office is equipped with one or more switch boards. 

Fig. 289 represents a section of a central office switch, and the connections for 
one circuit. The figure also shows a spare relay and battery, and the manner of their 
connections, as employed in some central offices. The spare set is used in case of 



DISTRICT TELEGRAPH SWITCHES. 



Z17 



trouble to the regular set, which is shown at r s. In the figure the regular set is shown 
as " cut in " by the phigs at x x. Should it be desired to displace the regular set and 
insert the spare set, the plugs are removed from x x lo z z. A call box cb is placed in 
the circuits in the central office, to test the circuit. Any circuit may be grounded in 
the central office by use of disc and plug on the switch at f f'. In Fig. 290 is shown a 
somewhat different form of central office switch, with three call box circuits, and the 
manner in which the local and switch connections may be made, b b b are the bell mag- 
nets. G G G, the i-eofister 

FIG. 289, ' ^ 

magnets, r r r, the 
relays of the three 
circuits. The bell and 
register magnets of the 
different circuits are 
connected in multiple, 
thereby requiring but 
one Leclanche battery 
LC. Each call box circuit 
is, however, supplied 
with separate gravity 
batteries, c c c. 

A test instrument^ 
for "grounds " is shown 
to the left of the switch 
s. By inserting a pin 
plug in both " straps " 
connected with any one 
of the circuits, one strap 
at a time, and by turn- 
ing the crank of t, if a ground exists on any circuit, it will be indicated on the bell and 
register. When the line is clear the action of the " test " box will be without effect 
on the relays. 

LOCKwooD BATTERY. — The form of main line battery most generally used in the 
district service is that known as the " Lockwood," the elements of w^iich are the same 
as in the Callaud gravity battery, namely, zinc, and copper in a solution of sulphate of 
copper. The only difference is in the shape of the jar and of the copper element. 
{see Fig. 291). The jar is about 12 inches high, by 5 wide. The copper element con- 
sists of two horizontal spirals of copper wire; one resting on the bottom of the jar, 
the other supported from the lower spiral* by a copper rod, or a narrow upright spiral, 
about as shown. The bluestone crystals are placed between the upper and lower spi- 
rals. The object said to be gained by the use of the upper copper spiral is that, in 
some manner, the " blue " solution is prevented from rising above it, and, thereby, the 
deposit of *' black " copper on the zinc element is minimized. But, perhaps, a better 
explanation, as regards the non-rising of the blue solution beyond the upper spiral, is 
that the battery, being on closed circuit the greater portion of the time, with a resist- 
an'3e of 150 to 250, or more, ohms, uses just about sufficient sulphate of copper to keep 
the "blue" line at the ric^ht heio-ht. 




DISTRICT TELEGRAPH SWITCH* 



0/ 



8 



AMERICAN TELEGRAPHY. 



A slight modification has somewhat recently been made in the construction of the 
copper spirals. Formerly, the two spirals and the supporting rod were made separ- 
ately and were held together by screw nuts. In the modification, the lower horizontjii 
spiral is continued up from its centre as a narrow vertical spiral, equal in length to the 




DISTRICT TULEGRAPH ClkCLTI ?— COXXECTIONS. 

rod previously used. A short piece of straiglit wire is continued down, from the cen- 
tre of the upper spiral, and is dropped loosely into the top of the narrow spiral rod, 
thus dispensing with all screws and screw nuts. In a very short time after the cell is 
set up, a firm connection between the spiral rod and the upper spiral is established by 
the deposition of metallic copper. 

The spiral form of copper element is used until it becomes too bulky for the jar, 
when the copper is disj^osed of. 

The Lockwood cell lasts from lo to 12 months without removal, in this service. 
Callaud, or gravity cells^ have been known to give satisfactory results for from 6 to 9 
months without renewal, in the district service. The solution in the cases referred 



LOCKWOOD BATTERY. 



379 



FIG. 291. 



to was prevented from evaporating and salts from forming, by the use of a thin layer 
cf a good quality of battery oil, placed on the surface of the liquid. 

It may be remarked, also, of the Lockwood battery, in connection with the dis- 
trict messenger service, that it has quite a presentable appearance and, therefore, it is 
frequently placed in central office window, or other conspicuous place, side by side 
with a register or two, thereby giving the office a *' professional" look that it might 
not otherwise have; the full significance of which remark will be best appreciated by 

those who are familar with some of the by-places in which 

District central offices are located. 

DISTRICT SERVICE TIME SLIPS. lu Fig. 392 is shoWU a 

chest of small drawers, numbered. In each drawer are placed 
slips having printed on them the name and address of the 
subscriber whose call box number corresponds with the num- 
bers of the drawer. Each drawer is partitioned, and thus 
affords space for two subscribers slips. The slip contains a 
space for the " number " of the messenger, the time the call 
is received, and the time the messenger returns. 

When a "call" is received the clerk on duty takes 
out a slip from the proper drawer, and after marking the 
time upon it hands it to a messenger. This slip is signed 
by the subscriber, and it serves as a receipt for the service 
l^erformed. 

It will be noticed that the numbers on the drawers begin 
at 3, and that no figure higher than 7 is used. This is to 
minimize the number of breaks on the wheel in the call box, 
as well as to save time in the transmission of the " calls." 




LOCiaVOOD GRAVITY CELL. 



FAULTS, ETC., ON DISTRICT CIRCUITS. 

Apart from " troubles" due to accidental line failure, which are many, in the dis- 
trict service, and which some of the companies have attempted to diminish by the use 
of insulated wire; and the troubles arising from the tempting nearness of the district 
wires, in many places, to the curious and meddlesome hands of messengers, porters, 
€tc., there are also the troubles due to such causes as the opening of the circuit by the 
introduction of high resistance in the " call " boxes, due to rusting of the break-wheel, 
or to the accidental stoppage of the wheel with the contact spring over a "break," etc. 

It is difhcult to provide a remedy for the tampering referred to and almost equally 
so to provide an absolute preventive of the opening of the circuit within the box. 
Probably the latter cause might be diminished by improving the mechanism of the 
call boxes, or by occasionally oiling it, although the amount of labor involved in the 
latter suggestion would most likely preclude its adoption. 

The use of relays of somewhat higher resistance and improved construction, 
thicker cores, etc.), has been found serviceable in reducing the number of " open " 
circuits due to the causes stated. 

In "hunting" for line trouble on a call box circuit it is customary first to ground 



38o 



AMERICAN TELEGRAPHY. 



the battery in the central office. The lineman then goes to the most centrally located 
call box and " grounds" the circuit at that point. This, if the trouble is an " open" 
circuit, puts in all the call boxes on one side of his ground. He then goes to a point 
somewhat closer to the central office and grounds that; if '' OK, " he then proceeds 
further from the central office, and so on, until the trouble is located between two or 
more boxes. 

FIG. 292. 

3 ^i) 4 — ~ '^~' ~~ — 




SERVICE SLIP DRAWERS, 



The first District messenger service system was established in this country about 
eighteen years ago, on a small scale. To-day it is estimated that there are over 150- 
000 call boxes in operation. When the service was inaugurated, a rental was charged 
for the use of the box in addition to the charge for the messenger's service,but, in or- 
der to secure business, competing companies, in the larger cities, undertook to sup- 
ply boxes free, and this is now the prevailing custom, except when "return signal " 
boxes, or other special signal boxes are supplied. 

This "service'' has quite recently and after much opposition been introduced in Lon- 
don, Eng. 



CHAPTER XXVI. 



Automatic Burglar Alarm Telegraphy. 

The object of automatic burglar alarra telegraph systems, or, as they are also 
frequently termed, " Electric Protective " systems, is to automatically announce^ by 
the ringing of an electro-magnetic alarm in a central office, the presence of intruders 
in the building, or buildings, in which the protecting apparatus is installed. 

FIG. 293. 




MS >f^ 



BURGLAR ALARM TELEGRAPH SYSTEM CONNECTIONS. 



One of the plans on which such systems are arranged is the following: In the 
" protected '' building a net-work of wires is run in partitions across doors, sky-lights, 
etc. These wires are a part of a circuit extending to the central office and the said 
wires, and the doors and windows of the protected building are so connected with the 
circuit that any interference with them after they have been " set," will cutout 
a high resistance, suitably placed in the circuit, which will so increase the current on 
the circuit as to operate an instrument at the main office; or, if the resistance is not 
*' cut out," but, instead, the circuit should be broken, by accident or design on the 
part of intruders, the absence of current, or even a diminution of it, on the circuit, 
will likewise cause an alarm. 

In Fig. 293 is shown a diagram of the electrical connections and apparatus em- 
ployed to carry out the requirements of the foregoing plan, which is generally know- 
as the Holmes burglar alarm system. 

THE HOLMES BURGLAR ALARM TELEGRAPH. 

The instruments, etc. shown at the left are supposed to be in the central or mam 

381 



382 AMERICAN TELEGRAPHY. 

office MS. Those at the right, of the building to be protected, BP. 

At MS X is a pointer carried by the neerlle ry armature of a galvanometer or 
relay m; the pointer being pivoted at x. i is the magnet of an ordinary indicator; 
FF, f'f' are metallic strips, normally separated from each other,, between which the 
metallic rods rr', are placed when it is desired to close the local circuits shown, or 
from between which the same rods are withdrawn when it is desired to open those 
circuits, b is an ordinary gravity battery, fb is a special battery, much stronger than b. 

At BP MR is a bell magnet. mg is an ordinary magnet. p, p may represent 
a net- work of wires running through a partition or elsewhere, e is a high resistance 
placed at some point in the building, s, s are arrangements of metallic strips connect- 
ed, as shown, to the circuit, and attached to doors, windows, safes, etc., in such a 
manner that when the doors or windows are furtively opened the strips are brought 
together, thereby short-circuiting the resistance e. 

The operation is as follows: When the circuit is in its normal condition, as shown 
in the figure, the resistance r is included in the circuit. This, with the resistance of 
the line and the magnets, gives a certain strength of current and, as a result, the 
pointer n. at MS, is brought to a position midway between the contact points ^,c\ in 
wliich position the local battery lb is open and the armature i' of the indicator i, re- 
mains at, or nearly vertical. The normal position of the pointer n is noted on the 
curved scale s', so that any marked deviation to the right or left from that point 
is observed by the attendents. When there is no current whatever passing through 
relay or galvanometer m, the pointer, by its own weight, is arranged to fall ; for in- 
stance, against contact c\ 

Supposing that the resistance e in BP has become short-circuited, the effect is 
to largely augment the strength of current liowing in the circuit, and the magnet m 
now draws the pointer n against the contact c, which act closes the local circuit lb. 
The magnet of i, being thereby attracted, permits the indicator i' to drop, in the 
well known manner. This indicator carries or discloses the signal number of the 
building from w^hich the alarm has come in. Concurrently with the falling of the in- 
dicator, a vibrating bell, which may be placed separately in the local circuit, or at- 
tached to i, as shown, is set in motion by the same battery and will continue to 
vibrate until one or both of the rods rr' is withdrawn, to open the circuit of lb. 

If, instead of the resistance r at BP being short-circuited as described, the cir- 
cuit should be cut or broken, all current would be removed from the line and the 
pointer x would fall against contact c, again closing the local battery lb; thereby 
permitting the indicator to drop and give the alarm. 

It will be seen that the circuit is also led up to the armature of mg at BP 
and that the lower stop of the same instrument is connected to the ground. While 
the normal current is on the circuit the armature of this magnet is held back by its spring, 
which is adjusted accordingly, but when the current is increased,if only momentarily,the 
armature is attracted, short-circuiting the wire, thus giving an alarm. The bell- 
magnet MB is used as a "signal-bell," to give pre-arranged signals, transmitted from 
the main office, at the regular opening and closing of the store, or building. This 
magnet is so adjusted as not to be operated by the battery b at any time, otherwise 
intruders in the building would themselves be warned. When the main office de- 



HOLMES BURGLAR ALARM TELEGRAPH. 383 

eires to ring that bell, the button, or key, k is depressed, thereby putting battery 
FB to the line. The occupants of the protected building respond to these signals by 
depressing the key k', after a pre-arranged manner. 

It will be understood that, in the system just described, a separate wire is run 
from the central office to each building to be protected and a separate set of alarm 
instruments is assigned to each of said wires in the central office. This insures that 
any tamjoering with the wire in that building, or at any part of it, will be at once 
perceived in the central office and an attendant will be sent to ascertain the cause. This 
may be termed a "separate wire" method. It may be said to insure as nearly as attain- 
able, the absolute protection of the building against the entrance of burglars. 

The actual resistance r, used in the protected building is unknown to any one, it 
having been taken at random from a number of unmarked coils; consequently, an 
attempt on the part of intruders to replace it, without varying the current of the 
circuit, prior to an entrance into the building, would be unavailing. 

The chief objection to the employment of the separate wire method is an eco- 
nomical one ; namely, the large number of wires necessary to be erected and maintain- 
ed. The objection to the use of a single "metallic circuit, or " omnibus " wire, on 
which all of the alarm apparatus in each protected building should be placed has, 
hitherto, been that, in the event of the omnibus wire breaking or grounding, the en- 
tire system would be rendered inoperative until the wire had been repaired. 

A system recently introduced and now in practical operation in this country, 
known as the Wilder duplex automatic burglar alarm telegraph, employs an omni- 
bus wire, and means to be presently described, for the transmission of alarms, regard- 
less of whether the wire is grounded or broken, within, of course, certain limits. 

THE WILDER DUPLEX AUTOMATIC BURGLAR ALARM. 

The devices just referred to as being employed in this system whereby alarm 
signals are transmitted to the central office, regardless of whether the wire is open or 
grounded, form what is termed its " duplex " feature. In addition to these devices 
means are also provided in the protected buildings whereby attempts to ground or 
short-circuit the wires m the building will be armounced in the central office; etc. 

The apparatus and electrical connections of a central office and protected build- 
ing are shown in Fig. 294, in which co is the central office, bp is a '• protected " 
building. In co, br, gr and mr are ordinary relays, termed, respectively, the " buzzer 
relay, "" ground relay " and " metallic relay, " because of the respective functions 
alloted to them, br and mr are in the main line circuit, gr is in a circuit to 
ground, in which is placed a battery b'. The armature of br controls a local circuit 
in which is placed a buzzer b, which is set in operation when relay br is opened. By 
means of the 3-point switch j, the buzzer may be disconnected when desired. Re- 
lay MR may control, by its armature, an ink recording register g. By the use 
of the 3-point switch s\ the ground relay may be placed in control of that register; 
normally it is so placed. As the ground relay is not in the metallic circuit it would 
not, ordinarily, be responsive to signals sent over that circuit, but, by the operation 
of a peculiarly constructed break-wheel in tlie protected building, the signals sent 
in from that buildinoj are received in that relav. AVhen a foreio*n " o-round " comes 



3^4 



AMERICAN TELEGRAPHY. 



in on the metallic circuit the ''ground " relay in co is cut out by the attendant and 
the metallic relay is then caused to operate the register. The central office is also 
equipped with a telephone set which is tapped on to the metallic circuit, as shown, 
and is prevented from grounding that circuit by the use of the condenser c, in the 
manner described in Chapter XXII. (Simultaneous Telegraphy and Telephony), /is the 
receiver, / the transmitter. By the use of the telephone the inspectors are able at any 
time to communicate with the central office from any point of the alarm circuit. 



KIG. 294. 




WILDER BURGLAR ALARM TELEGRAPH SYSTEI' 



T, in CO, is an instrument termed a " testometer". It controls a special, separate 
circuit running parallel with the alarm circuit and enters all the buildings of the sys- 
tem. By aid of the testometer and apparatus with which the protected building is 
equipped, an alarm may be automatically set up by the central office from any one 
of the protected buildings desired, or from all of them in rotation, in order to ascer- 
tain the condition of the wires in those buildings, and also to ascertain, speedily, 
the location of trouble on the omnibus wire. The manner in which these functions 
are performed will be described presently. 

The apparatus in the protected building is contained in one box. It consists of 
a break- wheel bw, a " release " magnet em, in control of the break wheel, a *' safety " 
magnet sm, whose armature at certain times operates the release magnet, and tm the 
"testometer" magnet, supplied with two armatures, one of which /.also, at times, 
controls the release magnet, causing it to send in an alarm or signal; the other arma- 
ture /', controls, by a " push and pull " escapement pe, and escape wheel w, a disc r>. 
On the periphery of d a small notch is cut. This notch is placed on different parts 
of each disc relative to the other discs of the systems, for reasons to be explained. 



WILDER BURGLAR ALARM TELEGRAPH. 385 

The wires distributed through the building, and the contact points at doors, windows, 
etc., are represented by ww, etc. 

Resting on the periphery of the break-wheel bw are two flat, flexible, metallio 
strips a and c. The break- wheel is composed of insulating material. Between a and 
<:, a rigid, metallic strip b, not touching the break-wheel, is placed. The strips b^ c, form 
part of the alarm circuit and, normally, they are in contact with each other, as 
shown. Strip a is connected to ground and, at rest, does not touch strip b. The 
break- wheel is operated by a clock-spring, which is wound up at intervals. This 
spring gives it a constant tendency to rotation, but it is prevented from rotating by 
the engagement of the escapement e with the pin / on the side of the wheel. The 
escapement e is attached to the armature lever l of the release magnet, as shown. 
When the release magnet is magnetized by the closing of its circuit at any point, 
the escapement e slips away from p, upon which the break-wheel is permitted to 
make one revolution, when it is held by the engagement of the other prong of e 
with another Din on the obverse side of the break-wheel. In making this revolution, 
the notches in the periphery of the break-wheel hive come under the ends of the 
strips a, c. c falls first into the first notch, thereby separating c from b and opening 
the metallic circuit, which, by opening the buzzer relay in the central oflice operates 
the buzzer therein. Presently c rides again on the periphery of bw, closing the me- 
tallic circuit, and the next instant the strip a falls into the same notch, thereby 
making contact with b and placing its " ground " on the metallic circuit, with the 
result that the " ground " relay in co is closed by the ground battery b', and the 
reo'ister g is operated. The next instant again, the strip a rises out of that notcli 
thereby removing the ground, and then strip c falls into the next notch, again opening 
the metallic circuit by separating b c, as before. This opening is quickly followed, 
also as before, by a grounding of the circuit, and with a similar result, and these 
actions are repeated until the last notch has passed both of the strips. The number 
of notches on the periphery constitutes the " number " of the protected building. It is 
thus seen that, normally, at each alarm, or at each revolution of the break- wheel, two 
sets of, or " duplex" signals, are transmitted; one by the opening and the other by the 
grounding of the metallic circuit. When, however, it happens that the metallic cir- 
cuit is broken at any point, it is obvious that the signal -will only come in on the 
" ground " relay. In practice, it may may be added, the main battery for the 
operation of the circuit is placed, in sections, at different points of the metallic cir- 
cuit, in the protected buildings, and the ground battery b' in the central office is dis- 
pensed with; since by this distribution of the main battery throughout the circuit it 
is clear that it will not matter which side of a building the wire may be open; 
there wnll still be battery between the ground in that building and the ground relay 
in the central office with which to operate that relay at such times. 

The release magnet will be closed if any of the doors or windows are opened 
after they have been set for an alarm. It will also be operated if an attempt should 
be made to short-circuit the wires of the building, as at h, co. This is due to the 
arrangement of the local circuits around the safety magnet sm, which is also in tne 
metallic circuit. The coils of its magnets are so wound that, ordinarily, the small 
battery b' will hold the finely balanced armature lever x away from the contact 



386 AMERICAN TELEGRAPHY. 

point ?/, but when the metallic circuit is short-circuited as stated, the division of the 
current that then takes place in the coils overcomes this balance and closes the local 
circuit of release magnet em, thereby permitting the break-wheel to transmit the box 
number. Of course, the presence of the short-circuit at h would prevent ther- trans- 
mission of signals by the openings of the circuit at b^ r, but the " ground "- signals 
would be transmitted as before. 

The operation of the '• testometer, " T in Fig. 294, may now be considered, it 
consists of a circular base, on which are placed small metal buttons d^ d^ etc. A 
aandle h^ pivoted at x\ may be passed over these buttons consecutively. As it passes 
from one disc to the next it opens the testometer circuit, in which one testometer mag- 
net TAi in BP, is indicated. The effect of these openings at bp is that the escapement pe 
is operated and the disc d is rotated. The lower armature / of tm is not, however, 
operated, although subjected to the same electrical action as lever /', partly because of 
an attachment, consisting of a vertical rod r, which, at its upper end, is normally 
in contact with the periphery of d ; partly by its greater weight. When, however, 
the notch on d comes opposite the rod r, and if it is then desired to lift armature 
/, a stronger battery is put on the circuit in co,and the lever rises into the notch tlie 
next time the testometer circuit is closed, and, in consequence, the local circuit 
of the release magnet km is closed at n', with the result that the box number is 
transmitted as before. Since then, as stated, the notch on each disc is at a 
relatively different position to that of every other disc, and, also, as the notch 
on each disc bears a certain relation to one of the flat buttons on the testometer in 
the central office, it is readily seen that an alarm, or signal may be brought in from 
any desired building. 

In BP certain metal segments marked i, 2, 3, 4 are shown. These form ordinary 
apertures for the insertion of " pin " plugs. They are contained in a small box lo- 
cated outside of the building. By their aid several functions can be performed. 
The 3-point switch n in bp is supposed to be turned to the left by the proper persons, 
on closing up tlie building for the night. Until this is done the door contact f, which 
is depressed as a signal for tlie closing of the building will not be operative. Hence 
in the absence of this signal, an inspector is sent to investigate the cause. He there- 
upon inserts a pin plug in aperture i, which, it will be seen, closes the house circuit 
around the points of the switch. 

By inserting a plug in 4, a pocket telephone, with condenser attachment, is con- 
nected to the metallic circuit, and, by its means, the central office may be communi- 
cated with. When it is desired to know the condition of the "safety" magnet, a 
pin plug, inserted by the inspector at 2, will elicit that information. A pin 
placed in 3 will test the condition of the door and window contacts. 

BfJRGLAR AI^RM AND DISTRICT MESSENGER CALL BOX COMBINATION. 

Sometimes it is desired to utilize existing " district'' service call boxes and the 
wires connected therewith, as burglar alarm circuits. 



AUTOMATIC BURGLAR ALARM TELEGRAPH. 



387 



One of the methods employed in this combination, known as the 
shown in Fig. .'295. 



Fix " box, is 



FIG. 295, 




COMBINATION "CALL" AND BURGLAR ALARM BOX. 



then sends in the "number" of the box to the central office; it 
being understood that ihe box signaling apparatus had been previ- 
ously wound in the usual manner, by means of the crank lever 
J, seen in Fig. 295^, and that the pallet had then been set by 
pushing up the rod v. This rod, comhig into contact with the pin 
T, which projects from the plate n. Fig. 295(3;, had turned that 
plate into the position shown in that figure. 

The burglar alarm circuit in the building to be protected 
may consist of wires w. Fig. 295, arranged in the manner 
described in the first part of this chapter. The joining of 
those wires will short-circuit the resistance k, thus, by means 
of a suitable battery b, placed in the building, attracting the 
armature and releasing the pallet p in the way already described. 

In some instances the current necessary to operate the mag- 
net K is derived from a " shunt " taken from the main circuit, 
thereby dispensing with the necessity for a battery in the 
j^rotected building, but the plan just described is considered 
more generally effective. 

THE DOUBLE BALANCF^D RELAY. 



The upper part of the box contains the 
lisual signaling apparatus of a call box 
used in the district service. The burglar 
alarm attachment is seen in the bottom of 
the box. It consists of an electro-magnet 
K, having a peculiar armature l which 
moves on a pivot m, sideways, to and from 
the core of the magnet. This armature 
carries a flat metal plate n (shown more 
clearly in Fig. 295^,) whicli plate lias a 
.notch on its upper portion. The pallet, or 
anchor i, which regulates the escapement, 
is provided with an extension r, whicli 
reaches down to the upper portion of the 
plate N. When the armature and, conse- 
quently, this plate,is in the position shown 
in Figs. 295, and 295^;, the pallet i is held 
against the wheel 11, ])re venting its 
motion. When the armature l is at- 
tracted and turns on its pivot, the 
notch is brought opposite the extension 
p, which, falling therein, thereby re- 
leases the signaling machinery, which 

FIG. 295 a. 




Another arrangement for indicating any 



change 



in the condition of a buro^lar 



3B8 



AMERICAN TELEGRAPHY. 



alarm circuit, known as a " double balanced " relay, is shown diagramatically in Fig. 
206. This instrument performs a practically similar office to that of tlae galvanometer, 

FIG. 296. 




DOUBLE-BALANCED RELAY THEORY. 



Fig. 293. The arrangement consists of two relays located in a central office of a 
"Protective" company. The main circuit is passed through each of these relays, 




DOUBLE-BALANCED RELAY, 



which are wound to about 150 ohms each. One relay, d, is so adjusted that the 
slightest decrease in the current will permit its armature to be withdrawn; the other 
I, is so adjusted that the least increase in the current will cause it to attract its arma- 



AUTOMATIC BURGLAR ALARM TELEGRAPHY. 389 

ture. lu the case of d the contact points are so arranged that the rising of its ar- 
matm-e will close the circuit of an annunciator, or alarm bell, cb. The contact points 
of I are so arranged that the lowering of its armature will close the annunciator. 

This arrangement makes it impossible to either *' open " or " ground " the " pro- 
tecting " circuit in the protected building, or elsewhere, without operating the alarm. 
In practice the relays are placed, for convenience, on one base, as shown in Fig. 297. 
The connections in the protected store or dwelling may be the same as those 
already described. 



CHAPTER XXVII. 



PRINTING TELEGRAPHY. 

THEOEY "step BY STEP " SYSTEMS NEWS TICKERS, ETC. 

Printing telegraphy relates to those telegraph systems in which telegrams, etc. 
are " printed " as received. 

Generally speaking, such systems depend, primarily, for success upon the uniform- 
ity of revolution of a cylinder or wheel at a transmitting station, with a type-wheel at 
a receiving station, virtually as in the instances of telegraph systems referred to in the 
Introduction. 

FIG. 298. 




" STEP BY STEP " PRINTING TELEGRAPH — THEORY. 

If, for example, two wheels of equal size, having on their peripheries ^* type " let- 
ters of the alphabet, are put side by side, and means are devised to cause them to rotate at 
equal rates of speed, it is evident that, if they start rotating, simultaneously, with a 
given letter at a given point, as long as the wheels rotate at equal rates of speed, each 
wheel Avill present a similar letter at the given j^oint. 

For instance, referring to Fig. 298. Suppose that below the wheels w w' are placed 
the electro-magnets m,m', with armatures and levers l, l' and paper tape passing between 
the wheels and lever. Assuming the wheels w, w' to have been set in rotation with, in 
each case, the letter a opposite a given point x. In that case a similar letter on each 
wheel will always be opposite x, and if the wheels are suddenly stoj^ped, and, at the 
same time, the circuit of the magnets m m' be closed, their armatures, will be attracted, 
and the upper end of the levers l l' will strike against the paper, impressing whatever 
letter may be opposite thereto. It will also be apj)arent that, in a similar manner, a 
dozju or more type-wheels of the same kind, similarly equipped with electro-magnets, 

390 



PRINTING TELEGRAPHY. 39I 

all in one circuit, might be caused to rotate synchronously, and, at a given time , sud- 
denly stopped and a given and similar letter be printed by each type-wheei. It is, 
however, a difficult matter to obtain a synchronous movement of two or more such 
wheels, especially when rotating at a high rate of speed, unless their rate of rotation is 
under control of some "master'' wheel or transmitter. Consequently, in electrical 
printing telegraphy, devices have to be resorted to which place the control of the 
type-wheels at the various stations, practically under control of a "sending" transmitter. 

In printing telegraph systems such as are used in the transmission of stock quota- 
tions, general news items, etc., and which are generally known as " ticker "systems, the 
type-wheel of the tickers in the various offices are placed under control of a transmit- 
ter which maintains them in synchronism by a " step by step '' movement, so called. In 
some other printing telegraph systems, such as the Phelps Long Distance, or " Motor,'* 
printing telegraph, the synchronous rotation of the transmitting and receiving wheels 
is maintained by a nearly synchronous rotation of the motors at each end of the cir- 
cuit, and in addition by a "correcting" device, (operated, primarily, by the transmit- 
ter,) applied to the type- wheel. 

The "step by step" movement is produced by a transmitter which sends out pulsat- 
ing currents, generally of alternate polarity, and apparatus responsive thereto. The 
pulsations thus originated cause the arnjature of a polarized relay to oscillate from side 
to side. As it does so it operates an escapement which, in turn, permits an escape- 
wheel to rotate one " step " for each oscillation; in other words, one half tooth for each 
alternate pulsation from the transmitter. The transmitting apparatus being under the 
control of an operator, a desired number of pulsations may be sent out. If, then, there 
should, for example, be 13 teeth on the escapement wheel, 26 pulsations would per- 
mit it to perform one complete revolution, the revolution being made ''step by step." 

In practice a type- wheel having 26 or more letters on its j^eriphery is placed on 
the same shaft as the escape wheel. If it should be started with, say, the letter a op- 
posite a given point, it would be an easy matter to bring, say, the letter d, opposite 
that point by the transmission of 3 pulsations, by the transmitter. In the same way 
any other letter on the type- wheel could be brought to the same point by the trans- 
mission of the requisite number of pulsations. Ordinarily there are twice as many 
characters on type-wheel as teeth on escape-wheel. 

In " step by step" ticker systems the transmitter is designed to send out, auto- 
matically, the requisite number of pulsations to bring any desired letter, on a distant 
type-wheel, opposite a given point, by the depression of a corresponding key of a key- 
board at the transmitting station. A theoretical diagram of a simple step by step 
printing telegraph system is given in Fig. 299. 

Several of the "ticker" systems now in use, for example, the Kiernan "news" 
ticker, is operated on, virtually, the principle embodied in that figui-e, excepting that 
the characters on the type-wheels and on the key-boards employed in the latter system 
are much more numerous than shown in the figure; in some cases as many as sc such 
characters being employed, these characters being composed of letters, fio-ures and 
fractions. This large number of characters, as will be obvious later, tends, however to 
diminish the speed of transmission. 

The transmitting apparatus of this system consists of a long cylinder t Fio- 299, 
resting on suitable bearings to permit rapid rotation. On the left end of the cylinder 



392 



AMERICAN TELEGRAPHY. 



shaft a metal segmental wheel w is mounted. At the right end of the same shaft 
there is an electric motor m, the shaft of which is connected by friction bearings to tne 
cylinder shaft. This motor drives the cylinder. The object of the friction bearings is 



FIG. 299. 




L^ 



Qii'iS 



SIMPLE •' STEP BY STEP ' PRINTING TELEGRAPH. 



to make it feasible to instantly stop the rotation of the cylinder without stopping the 
motor. The friction is so adjusted that, while, when the cylinder is rigidly held the 
motor may continue to rotate, the moment the cylinder is released the bearings insure 
the immediate starting(at, practically, its normal rate of rotation,)of the cylinfler. A 
centrifugal governor, not shown, attached to the motor shaft maintains its speed at a 
uniform rate. The motor is driven by a strong primary battery b. Any other suita- 
ble form of motor could, of course, be used. 

The cylinder t carries a set of blunt pins, or spurs, /,/, etc., projecting, spirally, 
from its surface. A key-board is placed above the cylinder with the keys directly 
over the pins, as indicated by the lettered discs. The pins project from the cylinder 



PRINTING TELEGRAPHY. 393 

at regular intervals from one another. There are as many pins as there are characters 
on the key-board. The keys are depressible and are provided with a catch, or spur, on 
their under sides. The cylinder is so placed with regard to the key-board that when 
any particular key is depressed, the projection under that key gets into the path of a 
certain pin on the cylinder, as it revolves, thereby instantly arresting the cylinder, at a 
given point in its revolution. 

The wheel w may be made in a number of different ways. The one shown in Fig. 
299 is divided in two portions, (each separated from the other, as at s, s',) by a zig-zag 
strip of insulating material /. The portion on the right is electrically connected with 
the hub x' ; that on the left with hub or. x and x' are also insulated from each other, 
A metal brush d rests on x ; a similar brush b' on x'. b is connected, as shown, to a 
positive pole of a battery; b' to the negative pole of a battery. A brush b rests on tlie 
periphery of the wheel w. The brush is so placed that, as the wheal revolves, it only 
touches one portion of the wheel at a time, b is connected with the line circuit. Each 
half section of w may be supposed to have, say, 13 segments, making in all on the peri- 
phery, 26 segments. 

As the wheel w is rotated one segment after another passes under the brush b. 
Since by this act the brush b is placed in connection lirst with, say, a positive pole 
of a battery and next with a negative pole of a battery, or vice versa, it must follow 
that, while the wheel is revolving, currents of alternate polarity will pass to the line, 
and, on the other hand, when the wheel ceases to rotate, a continuous current will pass 
to the line; the polarity of which will depend on which metal section of w the brush 
B comes to rest upon. 

As the wheel w is caused to revolve at a high rate of speed, the puslations must 
necessarily be very rapid, since for every revolution of the wheel, or the cylinder, there 
will be 26 electrical pulsations over the line. 

The receiving apparatus, or "ticker " proper, rs, consists of a polarized relay p r; 
*' press " magnet PM, which is an ordinary electro-magnet; a type-wheel tw, and an 
escape wheel Ew,on the same shaft, s. A drum d, by means of a weight f, and inter- 
mediate gearing, omitted in figure, tends to rotate the shaft. The rotation of the 
shaft is regulated by th<3 pallet, or escapement, e. The escapement itself is connected 
rigidly with an extension carrying the armature a of the polarized relay, and is piv- 
oted at p. The relays pm and pr are in the same circuit, as shown. Each relay is, 
consequently, subjected to every pulsation of current passing on the wire. These pul- 
sations are sufficient to oscillate rapidly the armature of the polarized relay, in conse- 
quence of which the pallet e permits a rapid rotation of the escape wheel and the type- 
wheel. 

As the polarized relay p r shown in Fig. 299, differs in form from those 
which have previously been shown in this work a few words of explanation concerning 
it may be of use. The armature a is permanently magnetized. Hence, it will have a 
north and south pole, p and r are ordinary electro-magnets, set with the ends of the 
cores facing each other, in the manner shown. Each magnet is so connected that a 
current of either polarity will make the poles facing each other of opposite magnetism, 
as indicated by the letters n s, s n. These poles, of course, change with each change 
in the direction of the current. As, however^ the magnetic polarity of the armature 



394 AMERICAN TELEGRAPHY. 

remains constant, it will be attracted from one side to the other with every alternate 
pulsation. By this arrangement a strong movement of the escapement is secm-ed. 

It has been assumed that the wheel w of the transmitter sends out 26 electrical pul- 
sations in one revolution. Consequently, one revolution of that wheel will cause 26 
oscillations of the armature of the polarized relay; in short, it will cause one revolu- 
tion of the type-wheel. Hence, if the transmitter be put in motion with the brush b 
resting on the segment which is in line with the space on the cylinder directly under 
key A, while the letter a on the type-wheel is opposite the platen p, on the end of the 
lever of the press-magnet pm, it will follow that, for every revolution, ov part of 
a revolution, the transmitter may next make, just enough pulsations will be sent out to 
permit the type-wheel to make an equal number of revolutions or parts of revolutions, 
and thus, whatever key may be depressed, the type-wheel will present a corresponding 
letter to the platen p. 

As the press-maguet is in the same circuit as the polarized relay, it might be 
exj^ected that it also would be responsive to the pulsations sent over the line, in which 
case it is evident that the platen would be continually impinging against the paper 
tape. This, however, does not occur, the armature of the press-magnet remaining open 
and j^assive during the continuance of the rapid pulsations. This is due to the greater 
inertia of the armature lever of the press-magnet, held back as it is by the strong re- 
tractile spring s, and also to the fact that the strength of the current is more or less 
diminished by an increased resistance, at the points of contact of the brushes with the 
segment wheel, during its rapid rotations. As soon, however, as the pulsations cease^ 
a stronger current passes to the line and the armature of the press-magnet is attracted, 
causing the printing of the desired letter, in the manner already indicated. 

It is, of course, essential to the success of such systems that the letters on the type- 
wheel should always be in a certain given position relative to the pins on the transmit- 
ter. When such is not the case, misprints of letters follow. This action is termed 
"throwing out." This may be caused by the sticking of the escapement wheel; a mo- 
mentary interruption of the line wire, etc. 

When printing telegraphy, or rather, " tickers," were first introduced, this defect 
was remedied as often as it occurred, by despatching an inspector to " set " the instru- 
ment in the various offices. Subsequently, an ingenious device for automatically 
bringing the instruments on a circuit to a " unison " point was invented by Mr. H. Van 
Hoevenbergh. 

Devices of this kind, termed "unison " devices, are now quite numerous.' In general 
they consist of mechanism which, when permitted to do so, throws ;». pin or brake in the 
path of a pin on the shaft of the type-wheels, in practically the same manner as the catch 
on the self -starting and stopping Morse register is brought into the path of the pin on 
the shaft of the fly-wheel. The pin is placed at a point on each " ticker " shaft which 
brings the type-wheel to a stop with the dot, or unison, type opposite the platen of the 
printing lever. The unison mechanism is not, as a rule, permitted to get into the path 
of the shaft pin until the type- wheel has made two or three continuous revolutions. 

Descriptions of " unison " devices employed in different ticker and other printing 
telegraph systems will be given subsequently. 

As premised, the foregoing remarks concern the simplest form of a printing tele- 



PRINTING TELEGRAPHY. 395 

graph system. It would be known in practise as a '^ single," or " one," wire and 
** single" type-wheel system, in contradistinction to systems in which two wires and 
two type-wheels are used. 

In stock quotations the use of figures is very frequent. Tlierefore, unless figures, as 
well as letters, were placed on the periphery of the type-wheels, it would be necessary 
to spell out the figures, which would be productive of slow working. When, on the 
contrary, the figures and fractions, as well as letters, are placed on a type-wheel, it 
adds many characters to the type-wheel and much reduces the rate of speed at which 
quotations, etc., can be sent, owing to the increased length of the circumference of the 
wheel. 

To avoid the delay which accompanies the spelling out of the figures, without at 
the same time reducing the speed of transmission by an increased circumference, a fig- 
ure wheel is, in many systems, placed side by side with a letter- wheel, and means are 
provided for printing from either the letter or the figure-wheel, at will. The manner 
in which this is accomplished varies with nearly every system . In some it is done by 
moving the type-wheels on the shaft so that either wheel desired comes over the platen, 
or printing pad,on the press lever. In others the platen is moved from below one wheel 
to the other, as required. In some systems, again, the platen is mechanically actuated; 
the result of an electrical impulse. In others a separate wire is provided to effect the 
result. The apparatus or wire employed for this purpose is termed the ''shifting" 
mechanism, or wire. 

While it is feasible to operate a two wheel ticker system on one wire, and many 
such systems are in successful operation, it has been found that when a large number 
of magnets are placed in the circuit the speed of transmission is diminished, which 
fact has led, in many instances, where fast working is necessary, to the use of a sepa- 
rate wire for the press-magnets. 



Gold and Stock Ticker System. 

The ticker system which is used by the Gold and Stock Company in "New York, 
and in other cities, for the transmission of stock quotations, employs in its operation 
two type-wheels and two wires, one of which latter is used to effect the rotation of the 
type-wheel shaft and to effect the printing of the characters; the other wire is used to 
effect the " shifting " of a pad from below one type-wheel to the other type-wheel as 
required. 

The transmitting or central office apparatus of this system is outlined in Fig. 300. 
The transmitting apparatus t is quite different, as to details, from that shown in Fig. 
298, but, in principle, it is practically the same. It consists of the motor bevelled 
wheels w,w'; cylinder c; reversing brushes /^, /^, etc. ; shaft s with arm e; a circle of 
magnets mc; a key-board kb; a " sliift " relay sr, etc. The cylinder c, rigidly mounted 
on the shaft s, is formed of hard rubber, around the surface of which, flat strips of metal 
m, m, etc., are placed. Above these strips are placed the brushes ^, Z^^, etc., which touch 
the strips in pairs, as shown. The brushes are attached firmly to the metal supports r., b- ; 
B^, B^. Brushes ^^ ^^, are connected to b. /^^ is insulated from Eg, as indicated by the 



396 AMERICAN TELEGRAPHY. 

black right angle; b^ is similarly insulated from b^ ; ^* is connected to b^, while b^ 
is connected to b^ ; and b'^ , b^ are both connected to b^. Brushes ^^ and b^ are con- 
nected together by a wire; brush b^ and brush b'^ are similarly connected (via sup- 
port B^). 

The poles of a battery, or dynamo machine, d, are connected to b^ and b^, re- 
spectively. The terminals of a type-wheel-press circuit are connected to b and b^. 

The eight brushes, with the strips m m, etc., on the cylinder, constitute the 
pole-changing, or current reversing, apparatus of a type-wheel-press circuit. In 
practice as many as 12 circuits are arranged for on one cylinder. The brushes for but 
2 circuits are shown in Fig. 300. 

The brushes b^, b'^, b^ and b"' are, it will be seen, placed in advance of brushes b^^ 
b"^, b^ and b^ , on the cylinder, assuming it to rotate in the direction of the arrow. 
The strips 7?t in^ etc., are so placed that the long brushes shall always be on their re- 
spective strips, together. Tlie short brushes are, likewise, arranged to be at one time on 
their respective strips. When the long brushes £re ^n the metal strips the short ones 
are on the insulated portion of the cylinder, and vice versa. As indicated in the fig- 
ure, the current through the press-circuit is, with the long brushes on the metal strips, 
in the direction outlined by the arrows. With the short brushes on the metal strips it 
will be found, on examination, that the current traversing the circuit will be in the op- 
posite direction. Hence, as the cylinder is rotated, currents of alternate polarity are 
sent over each circuit connected with the metal strips on its surface, and it will likewise 
follow that all the "tickers" in the respective circuits, being actuated by currents of 
similar periodicitv, will rotate in synchronism. 

This system, so far as the rotation of the type- wheels and the printing of impres- 
sions are concerned, is practically similar to the single wire system previously described. 
That is, the rapid alternate reversals of polarity on the circuit operate the type-wheels, 
and the prolonged current, when the reversals are stopped, actuatesthe press-magnet, 
which is too " blunt " to respond to the quick reversals. The cylinders are geared to 
run at the rate of about 150 revolutions, per minute. 

The cylinder shaft carries, loosely, on its left end, the bevelled wheel w. On each 
side of w, friction pads, or plates, f are caused to press, by suitable springs. Another 
bevelled wheel w', gears with w. The shaft s' is driven by steam or electric motors, 
and is the means whereby cylinder c is driven. It iy plain that as many cylinders as 
may be necessary could be similarly geared with wheels carried on shaft s' and when 
this is done, as it is in practice, all of the cylinders of the different circuits will be 
operated in unison. 

It is apparent that in this system the method of stopping the reversals must be 
different from that described in the case of the single wire system, inasmuch as the 
radially projecting pins from the cylinder, shown in Fig. 299, are here dispensed with ; 
and also as the key-board is removed from above the cylinder. 

In place of the pins on the cylinder the device outlined at the right end of the 
cylinder c. Fig. 300, is employed. This consists of a series of 36 electro-magnets mc, 
arranged in a ring and termed the " magnetic circle." Each magnet is provided with 
a movable core, one end of which is normally kept a short distance cut of the coil, 
or solenoid, by a stout spring s\ as shown at the right end of the magnets. The shaft 



GOLD AND STOCK TICKER SYSTEM. 



397 




398 



AMERICAN TELEGRAPHY. 



s of the cylinder carries, in proximity to the magnetic circle, an arm e, the end of 
which revolves close to the left ends of the electro-magnets in such a way that when 
any one of the coils is charged with a current, and, consequently, draws in its iron core, 
against the pull of spring s\ an extension of the core, which is thereby caused to pro- 
trude from the left end of the coil, gets into the j^ath of the arm r, arresting the motion 
of the cylinder, but, of course, not stopping the motion of the bevelled wheel w, which, 
continues its motion against the pressure of the friction pads.* 

FIG, 301. 




TRANSMITTER KEY BOARD. 



The key-board used in this system is a circular one (resembling that outlined in 
Fig. 301), with the figure and fraction keys in a circle within the letter keys. 

In Fig.300, a section, kb of the key-board, is shown ; with the "dot" key, and keys 
A b; also the "repeat" key, and numeral keys, i and 2. The frame-works of the letter 
and of the figure keys are insulated from each other. In this system, as in other ticker 
systems, the tickers of the circuit come to " unison" with a dot, or period, opposite 
the printing pad; and the key-boards of the transmitter, and the type-wheels of the 
tickers are so arranged that corresponding letters on each follow in a certain order. 

* The present practice (1899) is to employ a cylinder with spirally projecting pins ; the magnetic circle being dispensed 
with. Electro-magnets operated by the keyboard are arranged over the cylinder in such a way as to throw an armature 
in the path of one of the pins, thereby stopping the cylinder at a given point. Relays are then employed to control ihe 
various circuits analogously to the manner shown in Fig- 309 . 



GOLD AND STOCK TRANSMITTER. 399 

Thus, for instance, in Fig. 300, as the keys a b on the key-board follow the " dot " 
key, the letters a b will follow the " dot " on the letter type- wheel, of the ticker. 

In Fig. 300, one terminal of the coil of each magnet in mc is connected to the 
frame-work supporting the circle, and that frame-work is connected, by a wire w^, 
with the frame-work v of the letter keys, and with a battery d' in the same wire. 
Wire w2 is also connected to the frame v^, of the figure keys, via a relay sr. The 
other terminal of the coil of each magnet in mc is separately connected by a wire with 
a contact point a, b^ etc., under each key. Consequently, when a letter key, for instance, 
A, is depressed, it completes a circuit through magnet a. This magnetizes that magnet, 
thereby causing the interposition of its core in the path of arm r and stopping the cyl- 
inder and, consequently, the type-wheels, with the letter a in readiness to be printed. 
In the same way, if the dot key, or any other key, be depressed, the magnet connected 
with that key will interpose its core in the path of the arm, stopping the cylinder at 
the proper point. 

It will be seen that the contact points under the " figure " keys are connected with 
the contact point under some particular letter. For example, numeral i is connected 
with that of letter a, numeral 2 with b, and so on. It will be seen further that, when 
any of the letter keys may be depressed, it will complete a circuit including battery d' 
and its respective magnet, but will not include the relay sr; while, on the other hand, 
none of xS\q figure keys can be depressed without including that relay, as well as the 
magnet in the circle with which it is connected. For instance, if "figure " key i be 
depressed it closes a circuit containing relay sr and circle magnet a. Relay sr is the 
" shift ' ' relay. The function of this relay is to close an electro-magnet, by 
means of its armature lever /, in the "shift" circuit which runs through each ticker. 

The "shift" magnet in each ticker is so arranged that when the shift circuit is 
open, as is the case, normally, when " letters " are being transmitted, its armature lever 
moves the printing pad directly under the letter type- wheel ; while, when the " shift" 
circuit is closed, as it is when figure keys are depressed, the armature lever of the 
" shift " magnet in the ticker moves the printing pad directly under the figure type, 
wheel in the "ticker." The advantage of this device is that the shifting from letters 
to figures, and vice versa, is done automatically at the kpy-board, while in other sys- 
tems it is customary, first, to bring all the type-wheels to " dot," or unison, and then 
to depress a key which actuates the shifting mechanism. 

The " shift " magnet in the ticker will presently be shown and described (Fig. 302.) 
Referring to Fig. 300 again. It is frequently necessary in " ticker " service to 
repeat letters and figures. Ordinarily, to do this, it would be required that the 
proper letter or figure key, should be raised and again depressed to permit another 
revolution of type-wheel to bring it back to the same letter. In practice, however, 
this repetition of figures or letters is generally done by means of a " repeat " key, 
which controls a relay whose armature lever is included in the circuit. Such a relay 
is shown, in Fig. 300, in the "press and type" circuit. In this system, as has been said, 
the impression on the paper tape is made by the attraction of the press magnet when 
the rapid alternations have ceased. Consequently, until the rapid alternations of cm 
rent are again started, the "press " lever remahis up against the pad. When then the 
repeat key is depressed and released at the key-board, it opens the " repeat relay, 



400 



AMERICAN TELEGRAPHY. 



thereby opening the " press and type ' ' circuit, momentarily, which allows the press-mag- 
net in the ticker to open and close, whereby the armature lever falls and rises, and as, 
in doing so, it also actuates the paper " feed " mechanism, the particular letter is re- 
peated once or twice, as the case may be. When it is desired to hold the tickers idle, 



FIG. 302. 







GOLD AND STOCK TICKER. 

and at unison for a time, as when there is a lull in the market, the circuit closer CO 
around the dot key, may be closed, and the circuit opener co in the " repeat ' key cir- 
cuit opened, which will have the desired result. 

By means of the bevelled gearing on shaft s', in the central office, which insures a 
synchronous rotation of all the type-wheels in as many separate circuits as may be de- 
sired, and owing to the fact that coils of as many magnetic circles as there are cyl- 
inders employed may readily be connected in the local circuits controlled by the-re- 
spective letter and figure keys, and also owing to the readiness with which shift relays 
for each circuit may be placed in circidt with sr, it will be seen that one operator with 
one key-board may control all the circuits emanating from a central office. 

In the practice of this system dynamo machines are used in the central office as 
the source of electromotive force necessary. These are connected to the circuits in the 
usual manner, and resistances and fuses, not necessary to be shown in the figure, are em- 
ployed. 



GOLD AND STOCK TICKER. 40I 

"Wliere many " ticker '' circuits are thus operated simultaneously, some of them 
will vary as to length, number of instruments in operation, etc. It is found desirable, 
in order to obtain the best results, to bring about an equality between all of the cir- 
cuits, as regards resistance, lag, etc., and in some offices a "standard" instrument is 
placed consecutively in each circuit at the morning test, when the resistance of the cir- 
cuit is varied until the standard instruments respond in prescribed manner. 

Adjustable resistances, as at r^ R^, are placed in each circuit to facilitate any de- 
sired change in that respect. 

To avoid sparking at the transmitter, (which has always been more or less of a 
preventive of higli speed in printing telegraphy), condensers are very usefully em- 
ployed in different parts of ticker systems ; as at cr cr^. Fig. 300. A pawl/ and ratchet 
row the shaft s of cylinder c are employed to prevent backward motion of the cylinder. 
The circuits may be opened at o, o, by the removal of plugs. 

It may be noted that the circuits are operated in metallic circuit, as shown, it hav- 
ing been found preferable so to '• work " them. 

Duplicate, or spare cylinders and dynamos are at hand in the central office, and 
means are provided for quickly transposing from a regular to a spare set of apparatus in 
case of necessity. 

Scott two wire ticker — The Gold and Stock, or Scott, two wire *' ticker," 
is shown in outline in Fig. 302. 

PR is the type-wheel relay which is furnished with an escapement anchor e of the 
style shown. This escapement controls the escape wheel w, and, consequently, the shaft 
s and type-wheels t, t', in the usual way. 

Tlie shaft s is given a tendency to rotate by a weight and train of gearing con- 
nected with pinion /. pm is the press magnet whose armature actuates the long 
printing lever l. The relays PR and pm are in the same circuit. The lever l carries, on 
its side, in the manner shown, a pad f, which is movable on the small shaft s'. The 
pad F is held by the fingers//' of an extension e from the trunnion / of the armature 
A of the shift-magnet sm. When the shift circuit is open at the central office, as it is 
when letter keys are depressed, the retractile spring r withdraws the armature a of sm, 
from its magnet, which action turns the trunnion / of that armature so that the pad f 
is pushed under the letter type wheel. Thus, when the press lever l is operated, as it 
is when the rapid pulsatory currents are followed by a continuous current on the " type 
and press" circuit, and, also, when the repeat key is operated, only the "letter" wheel 
will make impressions on the paper tape. 

When, on the contrary, a figure key is depressed, the shift relay in the central office 
closes the shift circuit, and, hence, the armature a of sm is attracted, whereupon the 
fingers on extension e are caused to pull the pad f under the " figure " wheel, and away 
from tlie " letter " wheel, so that, when the press lever l is next operated, only figures, 
fractions or dots, will be printed on the tape. 

The unison device of this ticker is shown at u on the shaft s of the type- 
wheels. 

It consists of a spiral groove on the shaft, as indicated ; a metal strip h pivoted 
at o, normally resting in the spiral groove on the shaft ; a spring c', tending to pull 
this strip against a stop ?/; a pin p' projecting from the shaft s, and a rod x connected 



402 AMERICAN TELEGRAPHY. 

with the armature a' of the press-magnet pm. The rod n is curved so that it pasees 
under the shaft s, and yet, when the armature a' is raised, gives the strip h an upward 
lift, out of the groove. The operation is as follows : When the shaft s is rotated the 
spiral groove in the shaft moves the strip h towards the pin p', and in two or three 
turns the angular extension on strip h engages with that pin, checking the shaft s at a 
point where the " dot " characters on each wheel are opposite the printing pad. This, 
liowever, does not check the pulsations over the " type and press " circuit ; hence, when 
the dot key at the transmitting station is depressed, (which act causes a continuous cur- 
rent to be sent over the press circuit), the armature of P]vi,at the same time that it lifts 
the press lever, also lifts the strip h out of the path of pin p' on the shaft s, permitting 
the latter to rotate as usual. It will be obvious that when the press-magnet is 
operated continuously the rod x will continue to lift the strip h out of the groove and 
permit its spring c' to withdraw it to its stop u before it can be drawn in to the path 
of i3in p'. 

The paper feed mechanism is also operated by the press-magnet lever, practically 
in the manner described in the chapter relative to the !N^ew York Quotation Company's 
ticker (which see). 



The Phelps "Stock" Printer. 

This printer may be operated with one or two wires as desired. It employs two 
type-wheels; also two trains of gearing, one of which is assigned to the turning of 
an escapement Avheel ; the other to the turning of shaft s, which, when liberated, 
causes, in one revolution, the operation of the shifting and printing levers, and the 
paper feeding device. 

An outline drawing of the mechanism of the printing and shifting apparatus of 
the instrument as arranged for one wire is given in Fig. 303. 

In that figure pr is the polarized relay which, actuated by the rapid, alternate 
electric pulsations set up by the transmitter at the central office, controls the rotation 
of the type-wheels tw in the usual way. pm is a magnet, which may be termed the 
*'press-magnet," although it does not directly effect the printing. Like the ordinary 
press-magnet, it is only brought into action at the cessation of the rapid alternate 
currents. It will be found that the operation of this "printer" is almost 
entirely mechanical. 

The shaft s is given a tendency to rotation by the clock-work gearing 
alluded to. It is held in check by an arm a^ rigidly mounted on that shaft, 
as long as the spring lever h stands in the path of a. h is kept in that 
path by the flat spring s'. When, however, the armature lever a of pm is 
attracted by a continuous, or prolonged, current, it lifts lever h out of the 
path of arm a which act permits that arm to begin a revolution; but the 
same act that takes h out of the path of a, places ^ of a in the way of 
arm ^, at a point where it will have made about three-quarters of a revolu- 
tion; for a purpose to be explained. 



THE PHELPS STOCK PRINTER. 



403 



A wheel, w, carrying a crank roller r, is also rigidly mounted on shaft s, and, of 
course, revolves with it. sl is the shift lever of the " ticker. " pl is the printing 
lever. Both levers are mounted on a common shaft x. The right end of sl is slot- 
ted as shown. The crank roller R is placed in this slot. At its left end sl carries a 
3-armed shifter f, which is shown more clearly in Fig. 304. The printing lever pl, 
carries at its right end, on a short angular extension, not observable in Fig. 303, a 
small projection /. There is a nearly similar projection f placed on the wheel w. At 



FIG. 303. 




THE PHELPS "stock" PRINTER-THEORY. 

the left end of pl is carried a swinging frame, or fork, /, which latter carries a sliding 
shaft h^ on whicti the printing pad s^ and two discs d, employed in connection with 
the shifter, are placed. On the type-wheel shaft k, / /' are two pins that assist in 
shifting the printing platen. These last named parts will also be seen to better- ad- 
vantage in Fig. 304. 

The operation of levers sl and pl may now be readily understood. The act of 
partly rotating the shaft s turns the wheel 711. The latter, by means of its crank 
roller r, in the slot, depresses the right end of sl and elevates its left end, on which the 
3-arm shifter F, is carried. This effects the shifting of the printing pad, as will be 
further explained presently. It should be noticed here that when the wheel r*.' lias 
performed the half of its revolution the left end of sl is at its maximum lieight, 
and any further part of a revolution of 7v acts to depress f. This action results in 
throwing up the shift lever to effect the sliifting of the " pad," and then in effecting tlie 



404 



AMERICAN TELEGRAPHY. 




immediate withdrawal of the shifter out of the path of the pins / /', on the shaft k. 
The same motion of wheel w^ after it has performed half a revolution, ajid before 

the shaft s is arrested by the extension e^ brings tlie 
projection t' into contact with / on lever pl, which pro- 
jection /' gives that lever a quick momentary downward 
depression that throws the printing pad up against the 
type-wheel, thereby effecting an impression on tlie 
paper. The extent of the upward motion of pl, thus 
imparted, is regulated by an adjusting screw attached 
to the projection /, by which the latter may be raised 
or lowered. When the press-magnet pm is again re- 
leased the arm a of shaft s finishes its revolution and 
again engages with spring lever h, until the armature 
2^J^ oi PM IS again attracted. 

PHELPS SHIFTING DEVICE. The PHELPS PAPER FEED, — The paper " feed " of 

the Phelps printer is operated fig. 305. 

by the wheels pw and gs, Fig. 

303. In the operation of these 

wheels the mechanical move- 
ment employed is the Geneva 

stop. Small pins /^,/25 6tc., 

are placed on the side of the 

wheel PW at uniform distances 

apart. GS is a notched wheel ; 

the notches 11^ ;z2»etc.,of which 

are somewhat closer together 

than tlie pins/i,/2» ^tc, on 

PW. 



The wheel pw 
pause" wheel, 




termed a 

is geared 
with the clock-work, but has 
only a limited continuous mo- 
tion, namely, the distance 
between any two pins such as 
PiPi' It is released to begin 
this movement simultaneous- 
ly with the movement of 
the shaft s of the wheels. The 
direction of the movement 
of pw, is, however, opposite 
to that of shaft s. The wheel 
GS is mounted on an inde- 
pendent shaft S2, and is 
turned by the wheel pw. A roller wheel, pr, is mounted on the shaft 83, with GS. A 
smaller roller r (also seen in Fig. 303) rests on pr. The paper tape is placed between 
PR and r, in the ordinary way. 



PHELPS "stock" printer. 



THE UNIVERSAL OR EDISON TICKER. 4O5 

Normally, one of the pins say,/', rests in one of the notches n' of GS, as shown 
Consequently, when the wheel pw is turned, the pin f pushes the wheel gs out of its 
path, a certain distance, turning with it, necessarily, the roller pr, and moving with it 
the paper an equal distance. Then the pin leaves the notch ;/', while the wheel pw 
continues its movement. Por a moment tlie wheel gs is at rest, and the mechanism is 
so arranged that just at that moment the printing is effected. The next instant, as 
the wheel pw progresses, the ^\\\p^ goes into the notch n^ and moves the wheel gs 
with it to the end of its motion, thereby moving the paper forward another short space. 

Thus at every movement of the wheel pw, which occurs simultaneously with the 
movement of the printing mechanism, the notched wheel is moved around the distance 
of one notch, by the consecutive action of any two of the pins on Pw. 

Phelps shifting device. — The shifting and printing pares of the instrument are 
shown in Fig. 304, in which fw and lv/ are the ilgure and type-wheels, shown end 
on. K is the type-wheel shaft. / and /' are the '* shift " pins attached to the type- 
wheel shaft at points in alignment with the " unison " or shift dots, on the figure and 
letter wheels, which it may be said are necessarily placed diagonally to each other, as 
will be obvious later. Thus, looking at those pins from either side, along the shaft, it 
will be seen that one is slightly in advance of the other, f is the 3-arm shifter, piv- 
oted as shown, directly under the shaft k, on an extension carried from the shift lever. 
Consequently, the shift arms rise and fall with that lever, d and d' are discs, between 
which is placed one arm a' of the shifter f. 83 is a printing platen, or pad. The 
discs d^d' and the platen 83 are rigidly mounted on a sliding shaft h^ which is mov- 
able in bearings cut in the frame//, carried by the press lever pl. 

The transmitter of the Phelps printer is practically similar to that of the *' news '* 
ticker, described. But to assist in accomplishing the additional work caused by print- 
ing from two type-wheels with the use of but one wire, the key-board of the Phelps 
transmitter is provided with two dot keys, termed the *' letter " and " figure " key, re- 
respectively. These keys are placed directly over two consecutive pins on the trans- 
mitter cylinder, and each pin transmits a pulsation of different polarity. Hence, as- 
suming that the "letter " dot pin is placed one " step " in advance of the '' figure " dot 
pin, and that the " figure" pin /', on the type-wheel shaft, is one '^ step " in advance of 
the letter pin /, (considered from the direction in which the cylinder and shaft respec- 
tively rotate) it is clear that the said shaft will be rotated one " step " more, when the 
figure key is depressed, than when the letter key is depressed. 

It, therefore, depends upon the position of the type-wheel shaft whether the 
pin / or /' shall be in the upward path of the shifter f; and this, as just intimated, is 
regulated by the transmitter at the central office. 

It has been explained that f is momentarily raised with the lever si., by the 
action of the crank roller r on wheel iv. 

If, as in the figure, the shaft k be stopped, with the pin /' over the arm a of the 
shifter, the lower arm a\ by engaging with disc d when the lever sl is thrown up- 
wards, will throw the sliding shaft //, to the left and, with it, the platen So under 



406 AMERICAN TELEGRAPHY. 

tlie letter- wlieel. If, on tlie contrary, the shaft k be stopped with the pin/' over 
arm a^, the arm a will slide the platen under the figure wheel. 

To j^revent the paper from coming in contact with both wheels at the time of 
printing, a thin plate/ is inserted between the type-wheels and so placed as to extend 
slightly below them. 

Key-board, type- wheels, unison. — There is but one set of keys on the key-board 
of the Phelps transmitter (and others of a similar nature) for both the letters and 
figures; each key being marked with a letter and figure (or fraction.) For example, 
key A is also marked i ; key b is also marked 2, and so on. The characters impressed 
on the paper tape will, of course, then depend on whether the "figure " or *' letter" 
key has been last depressed. 

In the Phelps printer there are two parallel consecutive "dot" types on the 
" letter " and " figure " wheels respectively; the figure dot proper being placed diago- 
nally to, and one step in advance of, the letter dot, as already intimated. This, it will 
be found on consideration, insures that the character printed on tlie paper tape, imme- 
diately after each " shift," shall be a dot. 

The "letter" dot key on the key-board also serves as the "unison" dot key, 
(the unison device of the Phelps system being practically similar to tliose already 
described.) Consequently the unison stop pin on the type-wheel shaft is in direct 
alignment with the letter pin / over the shift arm. As the type-wheels of each ticker 
on the circuits are exactly alike and the unison pins on the type-wheel shafts are at 
corresponding points on each shaft, it follows that all of the ti(}kers will come to 
unison at a given point and tlius will be in readiness to rotate synchronously and 
each with a given character at a given point when the transmitter cylinder is again 
released. It is customary, in practice, to allow the tickers of a circuit to run to unison, 
at short intervals, to insure that if any machine has " thrown out, " its synchronism 
may be rectified. The type-wheels are brought to unison before shifting. 

The Phelps stock printer as it appears in service is shown in Fig. 305. In that 
figure cw, cw' are the winding wheels of the respective clock-works, to which ref- 
erence has been made, tw is the type-wheel, a the armature lever of permanent 
magnet pm. sl the shift-lever, etc. 



The Universal or Edison Ticker System. 

This ticker is in use in many American cities. It is a two wire system. It 
differs somewhat from those already described in several important respects. For 
instance, the type-wheel shaft is rotated by means of a " push and pull " motor, 



EDISON OR UNIVERSAL TICKER. 



407 



cperated by pulsatory, " straight " currents, set up by the transmitter. Thus, neither 
weights nor clock-work gearing is required /;/ the ''ticker". Again, the type-wheels 
(letter and figure) are " shifted " on their shaft so that either wheel may be printed 
from, at will. 



FIG. 306. 




UNIVERSAL OR EDISON STOCK TICKER THEORY. 



A portion of the transmitter t at a central office co and of a ticker at a 
branch office, with the parts somewhat separated and enlarged, for the purpose of il- 
lustration, are shown in Fig. 306; parts unnecessary to the description being omitted. 

The transmitter consists of a cylinder c, a portion only of which is shown, at tlie 
right of the figure. This cylinder is driven by any suitable motor, and it is stopped at 
any desired point in the well-known way, by the depression of keys on a key-board, 
not shown. On the left end of the cylinder shaft two segmental wheels w w' are 
placed. These wheels are made up of metal segments which are connected respec- 
tively with the hubs h h' . The segments are insulated from each other. /% /'' rest on 
the hubs of w and w', respectively. The other ends of these brushes are connected 



/}08 AMERICAN TELEGRAPHY 

with a common battery mb. Brushes b and b' rest on the wheels as shown. The 
urush B is connected with the press-magnet circuit. Brush b', with the type-wheel 
circuit. 

The metal segments on wheel w are narrower, it may be seen, than those on 
w'. There are as many segments on w as there are pins on the cylinder, but only 
half as many segments on w'; or, in other words, half as many segments as there 
are characters on the type -wheels of the ticker. 

As the cylinder rotates, the current from MB passes over both the ''type-wheel'* 
circuit and " press " circuit. 

In the ticker, at the left, tm is the type-wheel magnet, pm is the press-magnet. 
The type-wheel magnet in this ticker has obviously more work to do than is assign- 
ed to that instrument in the tickers of other systems, inasmuch as it is required 
to revolve the type-wheels, by means of its armature lever and the " push and 
pull" gearing shown; but, notwithstanding this, it is more readily operated than 
the press-magnet pm. 

Consequently, Avhen the cylinder is rotated, while the current from mb passes 
over both circuits, only the type- wheel magnet is actuated. The inaction of the j^ress- 
magnet at this time is aided by the narrowness of the segments on w, which, by 
diminishing the duration of the contact, tends to diminish the current passing over 
the press circuit. When, however, the cylinder is brought to rest the continuous 
current thereby permitted to flow over the press circuit operates the press lever. 

As there are but half the number of segments on wheel w' that there are charac- 
ters on each type-wheel, it is evident that half of the pins on the cylinder must be set 
opposite insulated sections of wheel w'. Therefore, when the cylinder is stop]:>ed with 
the brush b' resting on an insulated section of w', all of the battery from mb will 
pass over the press circuit. When, on the contrary, it stops with the brush b' resting 
on a metal segment the current from mb divides between both circuits. With a dyn- 
amo machine as the source of e.m.f. this would have no bearing on the working of the 
apparatus; nor does it when gravity battery is used except that it is necessary to 
maintain the current strength at a point where there is ample margin to operate the 
press magnet in either position of brush b'. It is, of course, apparent that two sep- 
arate batteries may be used if desired ; one for each wheel. 

The "step by step " movement of the type-wheels in this ticker, although effected 
by the lever l of tm, as it rises and falls, is ^practically the same as in that of the. other 
printers described. For example, it will be eeen that when the brush b' is on an in- 
sulated section of w' the lever l of tm is withdrawn by the retractile spring s. In 
the act of withdrawal the upper tine of the anchor Amoves the toothed wheel tw a 
space of half a tooth in the direction of the arrow. When, as the wheel w' rotates, a 
metal segment is next brought under brush b', the armature of tm in the ticker is 
attracted. This again causes anchor A to move the wheel tw a distance of one half 
tooth. There are half as many teeth on tw as there are characters on each type- 
wheel. Thus, since a "make" and a " break" of the press circuit moves the type- 
wheels forward two letters, or figures, it is plain that although there are on the 
wheel w' but half the metal segments usually employed, that wheel effects the same 



UNIVERSAL OR EDISON IICKER. 4O9 

i-eeult as the ordinary segmental wheel with alternating currents; that is, one revolution 
of w' effects one revolution of tw, and, consequently, one revolution of the type- 
wheels. 

The type-wheels are mounted rigidly on a sleeve o, which is movable lengthwise 
on the shaft K by the devices shown at the right of the type-wheels. These de- 
vices consist of a small 3-arm lever / pivoted at jt, and a link lever /'•, pivoted at x' . The 
link lever /' is attached as shown, to the type-wheel sleeve. Thus, if the 3-arm lever 
/ be rocked on its shaft x^ it will, through the intermediary /', slide the type-wheels 
back and forth. 

The shafts, on which lever /is mounted,is supported by an arm a rigidly attach- 
ed to the shaft k, so that, of course, the levers /and /' rotate with the shaft k. 

The type-wheels, while free to move, within certain limits, to and fro on the shaft 
K, are held in a definite relation to it by a bent pin/, connected at one end directly 
with the shaft and passing loosely through holes, or slots, in the frames of the type- 
wheels, as indicated. 

The shifting of the type-wheels is brought about as follows: 

A projection r from the press lever pl, carries two pins /, /'. One of these pins is 
behind the other a distance equal to that between any two characters on either type- 
wheel. 

If the type-wheel shaft be stopped with the lower edge of lever / directly above 
the pin /', it is seen that, when the lever pl rises to print, the lever / will be canted 
as shown in the figure, and the type-wheels will be pushed to the left. If, on the 
other hand, the shaft k be stopped, with the lower edge of / directly above pin /,, 
the lever pl, in rising, will cant the lever /in the opposite direction, thereby "pulling'* 
the type- wheels to the right. 

The apparatus is then so arranged that when the figure " dot " on the key-board 
is depressed it will cause shaft k of the ticker to be arrested with the lever / imme- 
diately over the pin /, in order that the wheels may be slid upon the shaft to that 
point over the paper where the "figure" wheel only will make an impression on the 
paper. The same motion mo zing the " letter " wheel out of the way of the print- 
ing platen. {See Phelps shifting device, page 405). 

When the letter " dot '' key on the key-board is depressed the shaft k will be 
stopped with the lower edge of lever /immediately above pin /,'and the letter wheel 
will, consequently, be placed in position for printing, while at the same time the figure 
wheel is removed from above the paper. Either wheel having, in this way, been " set,'^ 
the printing of either letters or figures may be proceeded with in the usual manner. 
By a device such as that shown in the Phelps "ticker," the type of but one 
wheel is permitted to make contact with the paper tape when the press lever is raised. 

The type-wheels are prevented from "sliding'* lengthwise when the shaft is 
being rotated, by the pin f and disc d, in the following manner: d being mounted on 
the same sleeve as the type-wheels, when the type-wheels are brought into the posi- 
tion for shifting, the slot s on d is opposite the end of r. Consequently, in tliat po- 
sition, D may be moved right or left, past f. But as soon as the wheels begin to ro- 
tate the pin f is either on one side or the other of the disc d, which, it will be seen 
prevents a lateral motion of the wheels at such times. 



4.IO 



AMERICAN TELEGRAPHY. 



FIG. 307. 



The unison device employed is practically similar to that described in connection 
with the "Gold and Stock " ticker and, therefore, need not be described here. 

The paper " feed " apparatus is shown at the right end of lever pl. It consists 
of a push " dog, " or pawl, which rests above a roller, over which the paper passes. 
The dog is operated by the bent lever pf, upon the shaft v, in such a manner that 
when the press lever is descending at the end under pf, the paper is urged forward. 
This action is brought about by the action of the pin <?" on the side of pl, in the slot o' 
upon the lever pf. 

It may be added that in many of the ''Edison" tickers as now operated, the 
shifting apparatus just described lias been replaced by that of the Phelps shifting 
mechanism, described in connection with the Phelps "ticker," the main difference 

being that, in the modi- 
fied Edison ticker the 3- 
arm shifter therein descri- 
bed is carried by the '"press' 
lever instead of the "shift" 
lever. 

The application of the 
Phelps shifter to the Edi- 
son ticker, it will be ob- 
served, dispenses with the 
sliding type-wheels on the 
shaft, the printing platen 
being moved instead. 

The Edison, or Univer- 
sal ticker, mounted on a 
base board and virtually 
as it appears in practice is 
shown iu miniature in Fig. 

307- 

Universal ticker trans- 
mitter. — The principle of 
another form of trans- 
mitter used with the "Uni- 
versal ' ' ticker, whereby 
the same results are ob- 
tained as by the insulated 
segmental wheels, is shown 
in Fig. 308. 

In this figure g is a cog-wheel on the shaft s, driven by an electro motor, 
weights, or a spring. On either side of g two smaller cog-wheels w, w', of equal 
8ize, are geared. On the shaft with w a toothed wheel a is mounted. On 
the shaft with w' another toothed wheel, a', is mounted. There are double the 
teeth in a that there are in a'. A lever / is caused to rest on the periphery of 
a; a lever /' is similarly placed on a'. The "press'' circuit is connected with 




EDISON OR UNIVERSAL TICKER. 



UNIVERSAL OR EDISON TRANSMITTER. 



411 



lever /; the "type" circuit with /', as indicated. A contact point c is placed 
adjacent to /; a contact point c' adjacent to /'. Owing to the manner in which w w' 
are geared to the wheel g, the rotation of eacli in the direction of the arrows is 
insured. As the wheels a a' rotate, it will be seen that lever / will make contact 
at c each time its end e falls into a notch between the teeth of a, and it will break 
contact when the end e rides upon a tooth, as in the figure. On the contrary, in the 
case of lever /' the contacts of tiie circuit are made at c' when the end e' is in a notch, 
and vice versa^ 

As wheel a has twice as many teeth and notches on its periphery as a' ; and since 
wheels w, w' rotate at a uniform rate of speed,it is evident that the " press'' circuit 



FIG. 308. 



J^ress CcfCccic 



Type Wheet Cu~ci^i/^ 




UNIVERSAL" TRANSMITTER, THEORY. 



will be broken at c twice as often as the " type " circuit at c' ; which, it will be noticed, 
is exactly the result obtained by the use of tho two segmental wheels, Fig. 306, one 
of which has twice as many metal segments as the other. Consequently, the action 
uj^on the type and press magnets of the "ticker"' is practically the same in both 
cases, as stated. 

In connection with the transmitter, Fig. 308, a key-board, the keys of which may 
be arranged in a semi-circle, as indicated at the left of Fig. 308, is used. A rod, or 
lever, L revolves with the wheel g, and arms beneath the keys are so placed that, when 
a key is depressed an arm directly beneath that key is thrown into the path of tho 
rod, or lever l. thereby stopping the wheel, and, of course, stopping the rotation of 
the wheels w, w', and, thereby, effecting a similar result to that accomplished by the 



412 AMERICAN TELEGRAPHY. 

depression of a key whose detent, or lower projection, intercepts a pin on the surface 
of the rotating cylinder of the transmitter, Fig's. 299, 306. 

As the rod l. Fig. 308, extends an equal distance in each direction from the cen- 
ter of G, it may be seen that, as one end of the lever leaves one end of the semi-circlej 
its other end will be at the beginning of the semi-circle and thus there is no motion 
lost by the lever, as a whole. 



The New York Quotation Company's "Ticker" System. 

In this system two wires and two type-wheels are used. One of the wires is used 
exclusively to operate the press lever and the shift mechanism of the tickers. To ope- 
rate the press lever the press circuit is simply closed momentarily ; to operate the shift 
mechanism the polarity of the current on the press circuit is reversed at the transmit- 
ting station. 

The central office transmitting apparatus and connections are shown in Fig. 309, 
PT is the " transmitter. It consists of a two-section shaft s', s,on which are mounted a 
trailer /, a ''clutch" wheel cw, and " pole-changer," pc. The shaft is driven by a 
belt on the pulley p'. The pole-changer is rigidly held on the shaft s', but it also rests 
on the shaft s by a friction bearing. This friction is normally sufficient to cause the 
rotation of the shaft s' with s, but, when a " clutch " c, shown separately in Fig. 309 
«, is advanced into the path of the teeth of the clutch wheel cw, the shaft s' is in- 
stantly stopped, while s continues to I'otate. 

At the end of shaft s', opposite the trailer /, a "sunflower" sf is placed. It is 
shown side view in the figuie. This "sunflower " is made in the usual way; being com- 
posed of a number of metal segments, which radiate from a co^nmon centre; the 
segments being insulated from each other. As the shaft s' is rotated the trailer passes 
over each segment in succession. A small section of the key-board used is shown at 
KB. A contact point/ is placed under each key of the key-board, and each of those 
contact points, with the exception of those under the keys marked f and l, is, by a 
wire, connected direct to a separate segment on the sunflower. The keys r and l are 
connected, in a round-about way, to one segment on the sunflower. The "pole- 
changer" PC is composed of a cylinder on the periphery of which metal segments are 
placed, as shown. Resting on this cylinder are three brushes, one of which is connected 
to a positive pole of dynamo machine d; another to the negative pole of another ma- 
chine D-", each through a safety fuse, and a resistance/-; while the middle brush is 
connected with a wire leading to a series of polarized relays, te, tr, etc., and thence 
to the ground at e^. The arrangement of the metal segments 'on pc is such that tlie 
middle brush rests on a segment jointly with each of its neighboring brushes, alter- 
nately. The result is that rapid reversals of polaritj^ are transmitted througli tlie 
polarized relays so long as the pole changer continues to revolve ; the consequence of 
which reversals is that the armatures of the polarized relays are kept in rapid o^icil- 
lation while the pole-changer rotates. The right and left hand" local" contact points 



QUOTATION COMPANY S TICKER SYSTEM. 



413 




J H- 



4H 



AMERICAN TELEGRAPHY. 



FIG. 30912. 



.^ 



of all of the j^olarized relays TR, TRetc, are conaected, respectively, to dynamo machmes 
of different polarity, as shown, for instance, in the case of the enlarged relay TR, 
whose contact points are in connection with dynarao machines d, d', respectively; 
the similar -connections of the other relays tr, etc., being omitted for clearness. The 
armatures of TR, tr, etc., are connected, as shown in the case of TR, through a switch- 
board, SB, with the type-wheel circuits. Thus so long as the cylinder, or pole-changer 
PC, rotates, currents of alternate polarity will be caused to traverse the type-wheel cir- 
cuits and will cease with the stopping of that instrument; these currents, in turn, rotating 
•and stopping the type-wheel shaft in each "ticker,-' in the usual manner, by means of 
polarized relay, controlling, by its armature lever, the escapement and escape-wheel. 

In printing telegraphy, in the transmission of signals at a high rate of speed, 
considerable skill is required on the part of the " operator '' to accurately gauge the 
proper duration of his finger on the keys of the board, to insure sufficient time for the 
correct printing of each letter. 

In the system in question a device has been introduced, by Mr. C. L. Healy, to 
"lock" the circuit of each key, the moment it is depressed, and keep it locked until 
after a letter or figure has been transmitted, when the key is, automatically, unlocked. 
By the use of this device, which will be described presently, it is only necessary that 

the transmitting operator should depress. his key for 
an instant, when the " locking " device comes into 
play, and holds the key circuit closed until the letter 
or figure is printed, without further thought on the 
part of the operator. 

When a positive current is passing over the line, 
the type-wheels of the tickers are " set ' ' to print 
letters on the paper tape. 

When figures are to be printed, a negative 
polarity is placed to the "press" circuit. One 
press circuit is shown at sb. Its source of e.m.f. is 
^ at D4 or D2, (right hand top corner in figure). It 

may be seen that the polarity of the current which will 
traverse the press circuit is controlled by the armature lever of the small relay rk; 
while the actual control of the press circuit is vested in the armature lever of another 
small relay pr'. At present it holds the circuit open, and the armature lever of re is, 
in the figure, arranged to permit the passage of a positive current. The " press " and 
the "type " circuits are grounded at the far end. 

So long as none of the keys on the key-board is depressed, the pole-changer pc, 
on the shaft s, s', continues to send out reversals of polarity over the type circuit, via 
the armature of the polar relay TR. (The case of one circuit only, need be considered). 
The manner in which letters or figures are transmitted by this system is as follows : 
Assuming the key k to be depressed. The sunflower trailer /continues to rotate until 
it reaches the segment connected with that key. The moment the trailer reaches that 
segment a current from dynamo d' passes via resistance r', through the clutch-magnet 
CM, (shown more clearly in Fig. 309^), thence to the frame-work of the transmitter,to 
the trailer, through the trailer and the sunflower segment to the key-board, thence to 




QUOTATION COMPANY TICKER. 415 

small relays SR, sp, to the 'Aground " at e. The completion of this circuit attracts the 
armature of cm, and its lever c (Fig. 309^) interposes a detent c before a tooth on the 
clutch cw, as in Fig. 309^, at once arresting the rotation of the shaft s, and holding the 
trailer on the segment connected with key k. At tlie same time the armature of small 
relay SR. is attracted and closes a circuit, partly indicated by dotted lines, and termed 
the " locker " circuit. This locker circuit, it will be seen, follows a route from the earth 
E-, and dynamo d', via the resistance r', and through the clutch-magnet cm, to the 
frame of the transmitter p t, whence it passes through the armatures of SRg and sr, 
to the frame of the key-board, thence through the coils of sk and sp, to the earth at e. 
This circuit keeps the clutch- magnet closed, regardless of whether key k is now de- 
pressed or not. Hence the name, " locker "circuit. 

The next action that takes place is the closing of the armature 2 of the relay sp, 
which completes a circuit from dynamo d', through that armature lever, to the magnet 
of relay SEg, thence to the tongue and lever of an ordinary continuity preserving trans- 
mitter T, to the relay pr', and the other "press " relays pr", to the earth at Eg. The 
completion of this circuit closes pr', and permits a charge from D4 to enter the press 
circuit, which charge actuates all of the press magnets on the ticker circuit, printing 
thereby the desired letter. Concurrently with the closing of relay pr', the armature of 
SRg has been attracted. This, it will be seen, closes a circuit through the magnet of 
a "release" relay sr^. The closing of this latter circuit, by attracting the armature of 
SK4, completes a circuit through the magnet coils of transmitter t and the coils of the 
" clutch-releasing" magnet rm, at the " printing" transmitter pt. The closing of this 
circuit, by operating the clutch-releasing magnet rm, withdraws the " clutch " from 
the tooth of the clutch-wheel, with which it had been engaged, permitting the shaft 
s', to at once resume its rotation. The " closing " of transmitter t, opens, at x., the 
circuit of the "press" relays pr'. At the same instant the current from dynamo 
d' is diverted momentarily through a resistance r, equal to the resistance of 
the "press" relay, (this to avoid sparking at .r,) and also through relay SRg, which 
again opens the " locker " circuit at armature SEg, thereby opening the small relays 
SR and sp. 

The re-opening of relay sp causes the breaking at armature 2 of the circuit from dJ 
which opens relay SR3. This, in turn, opens sr^, which again opens transmitter t, the 
opening of which at p opens relay SRg, and puts the circuit of the press relays pr', etc. 
into contact with x, at the transmitter t, in readiness to be again momentarily charged 
by dynamo Dg or d^, when relay sp is again closed. 

To relate in detail the foregoing actions necessarily occupies considerable space, 
but it may be stated that the actions of the different instruments occur so nearly simul- 
taneously, that the ear can scai'cely detect any lapse of time in the strokes of the 
levers. An idea of the rapidity of these actions will be gained by a consideration of the 
facts, that the shaft on which the pole-changer, clutch-wheel and trailer, are mounted, 
makes about 120 revokitions, per minute, and that the teeth of the clutch-wheel are less 
than one- half inch apart. Consequently, in order to stop the pulsations at a given 
letter, the armature of the relay cm must move into the path of a tooth in the g-gV(5 of 
a minute, there being 30 teeth on the wheel. The need, therefore, of a clutch which 
will respond without delay to the depression of a key, is obvious j hence, the object of 



41 6 AMERICAN TELEGRAPHY. 

the Healy " clutch " wherein a retractile spring is dispensed with, in order to avoid hin. 
derance to the quick forward motion of the clutch. By the successful operation of this 
clutch, one transmitter is made to operate all of the circuits of a system through 
" repeating " relays, as indicated by the marks at pr' and pr", each of which may re- 
spectively control a ' press " and "type " circuit, simultaneously with relays er andPK'. 

The relay SRg is termed a " time " relay, its function being to delay, momentarily, 
the releasing of the clutch, and the closing of transmitter t, until tlie printing of the 
letter has been assured ; to effect which properly the distance through which the arma 
ture of SR3 should travel is regulated by experiment. 

Quotation ticker shifting apparatus. — As already said, the '* shifting" mech- 
anism of the "ticker" of this system is performed by a polarized relay in the 
ticker. The mechanism by which this is effected will be described in connection with 
the ''ticker " itself. It need only here be said that, with a positive pole to the press 
circuit, the armature of a polarized relay in the ticker is so arranged as to hold at 
unison the " figure " wheel, while permitting the " letter " wlieel to rotate; while, with 
negative polarity to the press circuit, the same armature is so moved as to stop the 
*' letter" wheel at unison, while permitting the " figure " wheel to rotate in obedience 
to the impulses sent over the type-wheel circuit. 

The devices at the central office C O, whereby the desired " shifting " polarity is 
presented to the press circuit, are also shown in Fig. 309. 

The "figure " and the "letter" keys are shown, respectively, as r and l at kb. 
The contact points under both of these keys are, as already stated, and as may be seen, 
connected witli the same segment on tlie sunflower sf, but, in the case of key l, the 
circuit first passes through the coil of relay lr, while in the case of key f, the current 
first passes through a coil of relay fr. The segment on the sunflower, to which keys 
L. and F are connected, corresponds, as to relative position, with the unison " dot " on 
the type-wheels. In the figure, a positive pole is ready for presentation to the press 
circuit; and, hence, the ticker is set to print letters. Supposing then, the figure key f, 
to be depressed, the " current " from d' passes through clutch-magnet cm, arresting the 
sunflower trailer / at " dot " segment, then passes through the lower coil of relay fr, 
to the key- board frame, thence through relays sr and sp. The effect of closing fr is 
to close a circuit from dynamo d to the armature of fr, thence to the upper coil of fr 
and through the shift relays rr, pr, etc., to the earth at Eg. This attracts the armature 
of RR, which chai^ges the polarity from positive to negative. As long as the "letter " 
shift relay lr remains open the figure shift relay fr will be kept closed, by the upper 
coil on that relay. When, therefore, it is desired to shift back to letters, it is only 
requisite to depress the letter key l, which, it is seen, diverts the current from dynamo 
d', through relay lr, via the key-board frame, when that relay will be closed, breaking 
at V the circuit through relays rr, pr, etc., when the armatures of those relays will be 
retracted, and the positive pole will again be put to the " press " circuit. When a 
change from figures to letters or letters to figures, is to be made, it is, therefore, neces- 
sary to first bring the tyi)e-wheel to the unison dot. It may be stated that all of the 
apparatus shown in Fig. 309 is located in the central office. 

Referring to Fig. 309^ it will be observed that the arrangement of the *' clutch " 
magnet cm and "release " magnet rm is such that the attraction of the lever a (which 



QUOTATION COMPANY TICKER. 



417 



FlG. 310. 



is pivoted at a'), by cm, places the detent c in the way of the upper teeth, while the 
attraction of lever a by rm, withdraws it from those teeth. The small spring shown 
as apparently assisting rm is merely used to hold the lever loosely against its back 
stop when neither magnet is " active." 

QUOTATION COMPANY TICKER. 

The Quotation company's " ticker " is shown in Figs. 310, 311. In Fig. 310, t 

and t' are the letter and figure 
type-wheels, respectively. The 
shafts s s' of these wheels are 
arranged one as a sleeve over 
the other; the figure type- wheel 
shaft being the inner one. The 
shaft s' of the figure type- wheel 
has its bearings at x and x'. 
Shaft s has its bearings in / and 
t'. The shafts do not touch each 
other. Shaft s is geared by 
means of a pinion/' witli a large 
cog-wheel cw', both of which 
cog-wheels are geared with a 
train of gearing driven l)y 
weights. These weights give 
the type-wheel shafts a constant 
tendency to rotate. ew is an 
escape- wheel attached to shaft 
s. Ew' is a similar escape-wheel 
attached to shaft s'. These 
escajje-wheels are placed side 
by side, as shown, e, seen in 
end view, is an escapement 
anchor, which engages with the 
escape-wheels. This escapement 
anchor is connected witli the 
armature axis a of a polar- 
ized relay, pr, which is in the 
type-wheel circuit. The arma- 
ture of PR is given a lateral, vibrating motion by the reversals of polarity in the 
ty}K' circuit. Consequently, a corresponding lateral motion is given to the es- 
capement anchor e. The anchor is so arranged that when one end e of the anchor 
rests on a tooth on, say, escape-wheel ew, the other end, not visible in figure, rests on 
a tootli of Ew', and vice versa. Hence, accordingly as the relay pr is operated by 
the central ofiicc transmitter, the type-wheels will be permitted to rotate '• step by 
step, " in, practically, the usual way. 

In this system, however, but one type-wheel is permitted to rotate at one time, 




QUOTATION" COMPANY TICKER — END VIEW. 



4i8 



AMERICAN TELEGRAPHY. 



FIG. 311. 



means being provided, as already said, whereby either wheel is held at unison, as 
long as desired, while the other is free to revolve. This constitutes the shifting de- 
vice of this " ticker ". The holding of the wheels, as desired, is effected by means 
of projections v and v' from a rocking shaft Rs, which shaft is rocked by the 
armatui-e lever of a polarized relay sr which is in the "shift and press" circuit, the lat- 
ter controlled by the figure and letter keys of the key-board, in the central office. 

The i^rojection v, when in a 
certain position, as in the 
figiu-e, engages witli a pin w 
on the side of the escape- 
wheel EW. The projection 
v', in a certain position, en- 
gages with a pin w' on the 
letter wheel shaft s. In the 
figure v' and w' are clear 
of each other. Thus the fig- 
ure wheel is held and the 
letter wheel is free to ro- 
tate. This indicates that the 
letter key has been last 
depressed. When next the 
figure key at the central office 
is depressed, it will cause the 
closing of the shift relay er 
(Fig. 309) which places a 
negative pole to tlie line, 
thereb}?^ reversing the position 
of the armature of the relay 
SE, in the " ticker," and caus- 
ing its lever to rock the 
shaft SR into a position where 
it clears pin w and engages v' 
with pin w' , thereby freeing 
the letter wheel and holding the figure wheel. 

In this ticker, therefore, the pad is not moved, but strikes botli type-wheels at 
every impulse of the press lever. As, however, only one wheel is permitted to revolve 
at any one time, while,at that time, the oth^r wheel is held at "unison," tlie only 
impressions which appear on the paper tape are made by the dot type of the stationary 
wheel, and the desired characters of the revolving wheel. After a few impressions 
from the stationary dot type it ceases to mark on the tape, the ink on the pad giving 
out. The press magnet is not shown in Fig. 310. 

The manner in which the rocking shaft RS is operated will be evident on exami- 
nation of Fig. 310. The polar relay sr, is supported by the frame-work of the ticker. 
Its armature a, which is pivoted at x\ is polarized by contact with the permanent 
magnet pm, and hangs down between the pole-pieces of sr. At its lower end it 




THE BURRY SELF-WINDING TICKER. 4^9 

engages with an extension from rocking shaft RS in such a way that, as it oscillates be- 
tween tht pole pieces, it gives the shaft RS the rocking motion to which reference has been 
made. No device other than that for holding the type-wheel shafts by the rocking shaft 
KS, is employed to bring the wheels to unison, none being required, and this arrangement 
brings either wheel to unison within one revolution of the type-wheel, which fact 
adds to the speed at whicli the system may be operated, it being necessary, in some 
ticker systems, to allow 3 or more revolutions of the type-wheel to bring it to unison. 
This ticker is also shown, in side view, in Fig. 3 it, pm is the permanent magnet for 
relays pr and sr of Fig 310. tw are the type-wheels, pm' is the press-magnet, pl is 
the press lever, which extends to x and vibrates between the stops f, f'. p is the 
printing pad, which, raised by pl, impresses the character of the type-wheel on the 
paper tape, at each closing of the press relay pr', Fig. 310. The paper is drawn along 
between the rollers r, r, which are turned a certain distance at every motion of the 
press lever, i k and i r' are two ink rollers, placed as shown, one roller being assigned 
to each type-wheel. This arrangement of the ink rollers is designed to impart 
steadiness to the type-wheels. The type-wheels rotate at about 130 revolutions per 

minute. 

The paper "feed" is shown separately below Fig. 311 on the side of the upper 
roller r, a toothed wheel, between the teeth of which a pawl, carried on the printing 
lever pl, is placed. The pawl is so arranged that it slips past the teeth as the lever 
rises, while it engages firmly with one of them as the lever descends. The descent of 
the lever is thus caused to turn the roller, by which act the paper is drawn along only 
when the lever is descending, thereby leaving the paper at rest while characters are 
being impressed upon it. 

This '• ticker " as now developed is due chiefly to Messrs. Field, Healy and 
Mahnken. 



THE BUKRY SELF-WINDING TICKER. 

This ticker is in quite extensive use in the reception of general and pporting 
news. The instrument, as a whole, is shown in Fig. 311a. As its name indicates it 
is self winding, a spring being used to operate the type-wheel. The winding of the 
spring and the regular rotation of the type-wheel is performed by the press-magnet, 
through the medium of several ingenious devices, which are shown in detail in top and 
side views in Fig. 311^. In these figures the respective parts are indicated by num- 
erals. The main spring is enclosed in the drum 14, which is loosely mounted on the 
shaft 3. The spring itself is fastened at one end to shaft 3 ; its outer con\Tilution 
pressing against the top of the drum, tending to turn it by friction. The drum is 
fastened to the side of the cog-wheel 12 which is also loosely mounted on shaft 3, and 
meshes into the cog-wheel 7. A fly-wheel \t^ is also loosely mounted on shaft 3, 
and flexibly connected to that shaft by means of the spiral spring 1 5 which is fastened 
at the point 11 to the shaft 3, and at its other end to the pin 16 on the hub of the fly- 
wheel. A pin 17 which projects from the shaft into the path of pin 16 acts as a stop. 
This fly-wheel is the important feature of the self-winding process, as will be seen 



419'^ 



AMERICAN TELEGRAPHY. 



later. The gear- wheel 7 is loosely mounted on the type-wheel shaft 2, but it is flexi- 
bly connected thereto by the spiral spring 8, one end of which is connected to the 
shaft, the other end to the "wheel 7. This flexible arrangement is designed to avoid 
the jarring on this wheel due to the sudden stops and starts of the larger wheel 12. 

On shaft 3 a ratchet wheel 9 provided with a detent a, is rigidly mounted. A 
pawl 20, on the end of an extra Ijver 19, attached to the trunnion 4 of the printing 

magnet, engages with the ratchet 
wheel in such a marmf^r that, 
when the press magnet p is iu 
the act of closing, the ratchet 
wheel is rotated one or more 
teeth. This a^-tion turns shaft 
5. thereby moving pin 17 away 
from pin 16, It also, as it turns, 
winds spring 15 slightly. The 
inertia of Ihe fly-wheel holds it 
back for a moment, but present- 
ly it responds to the tension put 
upon it by spring 15 and starts 
forward, causing the pin 16 to 
strike against pin 17 with a ham- 
mer-like blow, thereby rotating 
the shaft 3 to a much great(r 
degree than is ihe case when the 
energy applied at the ratchet- 
wheel is alone relied upon, and 
thus the main spring on the 
same shaft is wound to a pro- 
portionately greater extent. 
In order to secure prompt ac- 
tion of the press-magrets of tickers it is necessary to employ a stronger current than 
would be necn-sary to operate them could a tardy action be permitted. This current 
varies ill difft-rt nt machines from about half an ampere to over one ampere. The 
Burry lic-kcr employs half an ampere. It is also known that the action of the press- 
lever is accelerated as it approaches the magnets, the speed beiag greatest at the last, 
and the stroke g nerally being stronger than is necessary for the actual printing. 
Advantage of these facts is taken in this self-winding arrangement to so construct 
the apparatus that the pawl on the end of the lever 19 does not engage with the 
ratchet-wheel until that lever nears the end of its stroke. Thus the self-winding ar- 
rangement not on'y does not obstruct the starting of the press-lever, but it also acts 
as a sort of cushion to the press-lever at an opportune time. 

The rest of the apparatus will be readily under.^tood. The tendenc}^ of the wind- 
ing arrangement is to the over-winding c.f the spring, but when this happens the 
spring momentarily slips in the drum,, and at such times the rotation of the type-wheel 
is kept up by the small spiral spring 8 on shaft 2. 







FIG. 311^. 












.^ 


^■l 


1 








-^■rsm" 




IC:" ;:-/V^' ',.■■ % 


f-Mmi 


% 










y;;-^^:;. 


''^^&- 


a 










s:jP^ 


'^K^^f^^i 


ita 


% 






i 


IH 


m 


\ 


\ 


1^ 




1 


ti 


1 ^ 


1 


1 


V 




. -^^^« 








■ 


^^^^ 




^ '^ 












-^ 



PHELPS MOTOR PRINTER. 



419^ 



Shaft 2 also carries tlie escapement-wheel 6, which is controlled in the usual way 



by the polarized relay, seen in 
Fig. 31m.. 

The keyboard and transmit- 
ter of the system on which this 
ticker is employed, are in a meas- 
ure akin to those shown in Fig. 
309, simplified, however, in some 
respects and modified in others ; 
the sunflower trailer and the shaft, 
which in Fig. 309 are operated by 
a pulley driven by a belt, being 
operated in the Burry system by 
an electric motor attached to the 
end of the shaft, and, instead of 
the clutch magnet, a pair of 
curved, soft iron armatures are 
mounted on the shaft and nor- 
mally revolve in the concaved re- 
cesses of a pair of coilf^, which, 
like the clatch magnet, have cur- 
rent sent through them when a 
key of the keyboard is depressed, 
with the result, in the present 
case, that the curved iron arma- 
tures instantly stop in the path of 
the magnetic field of the coils, 
therebv holding the shaft and 
sunflower i^i the desired position 
until the key is raised. The shaft 
is, of course, in frictional conntc- 
tiou with the motor shaft. 



FIG. 3 1 1/5. 




The Phelps "Motor" Printing Telegraph Syste 



M. 



This system is successfully employed on several long circuits of the Western Union 
Telegraph Company. This "printer," presumably, derives its distinguishing name from 
the fact that it was the first to be driven by an electric-motor in this country. 

The message as received on this " printer " is printed on a strip of paper in 
Roman letters. No figures are placed on the type-wheel ; the Romau numerals, such 
as YL for 6, being employed. 

This system, in common with other more or less similar ones, depends for its suc- 
cessful operation on synchronous rotation of the transmitter at one end, and the re- 
ceiver at the other end of the circuit. As will be shown, the receiver is not actuated 
by the " step by step " movement, as in the case of the stock quotation instruments 
described. 

The instruments, etc., employed in the operation of this system are shown, as ar- 



420 



AMERICAN TELEGRAPHY. 



ranged in practice, in Fig. 312, in which t represents the transmitter, which consists of 
a key-board, and mechanism controlled thereby to actuate a circuit breaker pc ; a 
receiver e, wliich comprises an electro-magnet, or relay, controlling a type-wheel and 
printing mechanism. The key board is clearly seen. m is the case containing the 
motor, MS is the motor battery switch. The motor, by suitable gearing, causes the 

FIG. 312. 




PHELPS "motor" printer. 

rotation of both the transmitting and receiving mechanism. 

Fig, 313 represents, theoretically, the electiic-motor connections and those of the 
transmitter. The motor employed in this system, due to the late Mr. G. M. Phelps, is 
highly ingenious and efficient, but as a description of it is not essential to an under- 
standing of the system proper, the motor is indicated in the figure as an ordinary 
drum armature. The route of the motor circuit may first be considered. Starting 
from the negative pole of battery b, it reaches, by means of an insulated wire, the in- 
sulated point p; thence it passes to the lever r, which is insulated from the frame- 
work. The circuit then passes to the wheel fd, which rotates in an oil pot op ; thence, 



PHELPS MOTOR PRINTER. 



421 



via the framework of the motor, to the motor brush and through the motor to the bat- 
t-ery. The function of the shunt wire w via r, will be described presently. The lever 
F rests more or less lightly on the periphery of fd, according to the pressure applied 
to the spring s by the screw h/ which may be turned up or down by the handle h. 
Motor Goveknor.— In order that the rate of rotation of the revolving apparatus 



FIG. 313. 




PHELPS "motor" printer, theory. 

at each end of the wire shall be practically the same, it is necessary that the speed of 
^ach motor should be under control at each station. This control is effected by means 
of an electro-mechanical governor, shown as g Fig's. 312 and 313, and consists of the 
following parts : A nearly solid wheel sw, (Fig. 313), forming part of a shaft s, as 
shown. A strip sc, and a rod m which passes through and above the upper part of shaft 
s, where it reaches, but is insulated from the lever f. The wheel sw has a segment s.^, 
which is fastened to the wheel by a stiff, flat spring fs. Wlien the shaft is in rotation 
this segment tends, by centrifugal action, to fly outward at a tangent, but ag the spring 
J f prevents it from doing so, it takes a downward movement, as indicated by the 
arrow. As it does this, the right end of the flat strip sc is given an upward tendency. 



42 2 AMERICAN TELEGRAPHY 

This causes the rod m^ which is resting on sc, to raise the lever f. This latter action 
separates wheel fd from lever f, and thus diverts the entire current through resis- 
tence e, thereby at once weakening the current in the motor coils. As the motor has 
considerable work to do in driving the transmitting and receiving apparatus, which it 
does by means of pinion pn on shaft s and cog-wheel cw, its motion is at once retarded, 
and the "governor" section sx of wheel sw, resumes, under the pressure of its support- 
ing spring, its former position, when contact is again made at fd and increased current 
js again supplied to the motor. In the operation of the motor this action is constantly 
taking place, but the governing mechanism is so prompt in its adjustment that the actual 
variation of the speed of rotation is not perceptible. 

The motor shunt, e, also serves the purpose of preventing sparking at the point of 
junction of the lever f with the wheel d. The resistance e is regulated to obtain the 
best results, and requires to be varied at times to meet the varying condition of the 
motor battery. 

Teansmitting Apparatus. — The key-board of the transmitter, as shown in Fig. 
3 1 2, contains the letters of the alphabet, a " dot " key and one " space," or blank key, 
that is one key which, when depressed, does not cause a letter to be printed, but yet has 
the effect of advancing the paper at the receiver. Each key is mechanically connected 
with one of a series of vertical slide rods, arranged in a circle within the hollow 
cylinder T. Two keys a, j, ana their respective slide rods sr, sr' are shown to the 
right of the motor in Fig. 313. From the upper end of each rod an arm a, a' extends, 
at right angles to the rods, towards, but not reaching to the centre of the cylinder. 
The act of depressing a key elevates its slide rod a certain, short distance; the angular 
arm being of course raised with the rod. A vertical shaft s' (Fig.313) rises through 
the centre of the cylinder. A hollow cog-wheel w is rigidly attached to the shaft. 
The shaft s' is tubular from the wheel w, up, and through this tube a small rod r, 
passes, as indicated by the dotted lines. One end of a bent lever cl, rests on the top 
of this rod. The other end of the lever carries a small roller which rests on an arm 
projecting from a rocking block rb, of the circuit breaking apparatus. 

RB carries a contact point at each of its 4 corners. Its upper half is insulated 
from the lower half; the line wire being connected to the upper half, the ground to 
the lower half. The block is pivoted at its centre. The levers l l' each have two con- 
tacts capable of connecting with the contact points on rb. These levers are inclined 
towards eb, by springs ps, ps'. Normally, the springs attached to eb give it the 
position shown in figure. When, however, the rod r' is raised, as it is by the action 
of depressing a key on the key-board, in the manner presently to be described, the 
bent lever cl, is caused to bear upon the projecting arm of rb; thereby partly turning 
RB on its axis. This action, it will be seen, transposes the contact points and reverses 
the battery b' ; for, as thus arranged, the circuit breaking apparatus is really a pole- 
changing device. At the distant end is a polarized relay, whose armature controls a 
rotating printing wheel. 

Hence, when the bent lever cl is operated it virtually controls the distant printing 
mechanism. 

The mechanism by which the circuit breaking apparatus is operated, is 



PHELPS MOTOR PRINTER. 



423 



FIG. 313 a. 



^^^ 




shown at the right in Fig. 313. It consists essentially of a small wheel h and its 
attachments, carried loosely by the shaft s'. (This wheel is also shown in Fig. 315). 
In shape it resembles somewhat a hat; having a flange f at the part corresponding to 
the rim. In Fig. 313 a, the wheel h is shown straightened out, for the purpose of 

better illustration. Above the crown, on 
the side of the wheel, there are four small 
elevations or ridges, e. On the side of the 
wheel are four u shaped niches, /. The 
extensions e and niches / on the side of 
the wheel are in virtually the position indi- 
cated in the diagram, as regards each other. On the rim of h an attachment d, termed 
a dog, is j^i voted at x. r is a projection which may be termed an ear. The actual 
shape of d is better shown in top views. Fig's. 315, 316, in which d is the dog, r the 
ear, / the tail, h the head, and p a tongue extended within the wheel through one of 
the niches /. 

Kormally, D is in the position on the flange shown in Fig. 316, and it is held 
snugly in that position by means of the curved tongue p and the jockey roller 7, at- 
tached to the inside of the wheel h. 

When, at certain times, the head h is pushed out, as in Fig. 315, the tongue is 
slipped over the roller, and thus the head is held out until it is pushed back again in 
the course of the operation of the device. This roller may be said to perform a practi- 
cally similar work in this device to that of the jockey roller in the Wheatstone trans- 
mitter. 

Normally, the wheel h and its attachments revolve with the shaft s' and wheel 
w. It is caused to do so by the device shown in Fig. 314. This represents the sides 
of the wheels w and h oj^posite to those 
shown in Fig. 313. A portion of the hollow 
wheel w is cut away for illustration ; k is a 
small projection from a spring rod n, the 
latter attached to the inside of wheel w^; k' 
passes out of the wheel w through a suit-^ 
able slot, just above the outside edge of the 
periphery of wheel h. The spring rod n 
gives K a tendency to press against the out- 
side of H. Thus, if the wheel h be stationary 
while w is moving, k will fall into that one of the four niches / on the side of h at 
which it first arrives, and will hold with sufficient tenacity to, at once, set h into rota- 
tion with w. If, however, the course of h be suddenly checked, k simply rises out of 
the niche, leaving the wheel h behind. But, again, if by the time k reaches the next 
niche, ear r has been released, k at once drops into that niche, and instantly draws the 
wheel H with it. 

Reverting now to Fig. 313. The wheel w is supposed to be rotating in the direc- 
tion indicated by the arrows; h being rotated with it. The angular arm a of tlie slide 
rod SR is shown as just having been elevated by the depression of key a. It will be 
seen that the angular arm a is now directly in the path of the ear /- of the dog which is 



FIG. 314. 




424 



AMERICAN TELEGRAPHY. 



FIG. 315. 




riding on the flange f of wheel h. The next instant the ear will strike against thatarrt, 

and throw the tongue out of a hole / on the side of h. This act throws the ear between 

two of a circular row of teeth (Fig. 315) which 

teeth are fixed just outside of the normal path 

of the ear. These teeth are cut in a circular 

metal plate z supported from the inside of the 

cylinder. This contact at once stops the rotation 

of H, but the wheel w continues its motion, the 

projection k having glided out of its niche. The 

result is that,- in a moment, a small j^rojection (v 

^ig- 3'^ 3) carried on the end of a rod o, and which 

extends below the under side of the wheel w, nor- 
mally resting in a depression d on the top of the 

side of the wheel Wjslides up on an extension e. This 

raises the horizontal rod o on which the vertical 

rod r' is resting as shown, and by that act the cir- 
cuit breaking, or current reversing apparatus, is 

operated in the manner above described. The length of time during which the rod 
R keej^s the circuit open, or reversed, corresponds with the time 
taken by the projection v to ride over the extension e. The in- 
stant it has done so it falls into the next depression and the rod r' 
falls with it permitting the circuit breaking apparatus to resume its 
normal position. 

The pulsations necessary to print the letter corresponding 
with the key which had been depressed at the sending 
station, having been transmitted, it is now necessary that the 

dog should be promptly released from the tooth which is holding it, that it 

may be ready to engage with the next slide arm 

elevated for the purpose of sending another letter. 

This release is brought about by the device of 

suspending from the bottom of the under side 

of wheel w, four small wedge-shaped metal 

pieces, with the point of the wedge towards the 

shaft s. These are shown as p,p,p,p, in Fig. 317, 

looking at them from below. Two of these 

pieces,/,/, are also shown in Fig. 313. They 

are so placed with relation to the' upper part of 

the ear r that, after the lower part of the ear has 

been struck by the angular arm a and the wheel 

H is, consequently, halted in its progress, the 

wheel w can only traverse a space equal to the 

distance between any two of the pieces, say, ad, 

when one of them will impinge against the ear r, 

thereby partly turning the dog on its pivot and detaching the ear from between the 

teeth Q. At the very instant that this happens the extension k, on the side of wheel 




FIG. 317. 




PHELPS MOTOR PRINTER. 



425 



FIG 318. 



t^ opposite the dog, (Fig. 314) has arrived at and dropped into one of the niches / on the 
side of wheel h, which at once compels the latter wheel into rotation with w, when it is 
again ready to perform its part in the transmission of another letter. (In Fig. 315 
the dog is shown as engaged with teeth q; in Fig. 316, free from the teeth.) 

Tims the act of stopping the wheel h, by the action of the angnlar arm 01 the 
slide rod, and the act of starting it by the action of metal piece p must occur within a 
very short time of each other. The shaft s' rotates at about 180 revolutions, ^er min- 
ute. As there are but four pieces, /, etc., the actual time would be but the one- 
twelfth of a second, and as each of the extensions e,e,e,e, occupies but one-eighth of 
the circumference of wheel h, the time during which the rod r' is raised is, virtually, 
but the one-twenty-fourth part of a second. 

Notwithstanding the speed of rotation of the shaft s', and the high rate of 
transmission by this system, namely, 65 to 75 words, j^er minute, it is worthy of note 
that the actual number of pulsations transmitted over the wire is much below that 
necessary in simple Morse telegraphy. For example, in transmitting the word 
"Phelps," by the Morse alphabet, 19 pulsations are necessary, while but 5 pulsations 
are required in the transmission of the same word by the printing mechanism under 
consideration. 

RECEIVING APPARATUS. — The cMcf pai'ts of the "printing" apparatus of the 
Phelps printing telegraph system are shown in Fig. 318. 

EM is an electro^magnet in a local 
circuit controlled by a polarized 
relay, l is a lever, to which is 
attached the armature of em. This 
lever has, at its lower end, an 
angular arm, or detent, d, which 
engages with the spurs, or teeth, 
s,s,s, of a star-shaped wheel, pw. 
This is termed the printing wheel. 
Six such spurs project from pw. 
On tlie end of each spur is an angu- 
lar arm a. At about the middle 
of each spur is a pin p. On the 
main body of wheel pw are six 
pins Vj^,V2, etc., the use of which 
will be explained shortly. The 
wheel PW is loosely mounted on 
the shaft x. 

Tlie flat wheel f is rigidly 
mounted on the same shaft, pw is 
pressed snugly against f ana when it is not restrained bv the eno-ao-ement of the detent 
D With one of its spurs, it revolves in unison with f. tw is the type- wheel, carrying the let- 
ters of the alphabet on its periphery, st is a toothed wheel, rigidly fastened to the t yi>o- 
wheel, so that, when, by proper means, the detent d of the lever e, whicli is fil 
crumed at n, is inserted between any two of the te^th of st, the ty|)e-wheel tw at 




426 



AMERICAN TELEGRAPHY. 



once ceases to revolve. Normally, the type-wheel tw is caused to revolve at ? 
rate equivalent to that at which the wheel h carrying the dog d at the transmitting 
station is rotated ; for simplicity the train of wheels for the purpose is omitted in 
Fig. 318. iw is an ink-roller which is held by means of its flexible support fs and 
a suitable spring against the types of tw. pl is a lever, the effect of whose operation 
is similar to that of the press lever of the ordinary stock printers. 

Normally the printing wheel pw is held at rest by reason of the fact that the 
local circuit controlling em is open and consequently its armature is withdrawn by 
spring s, thus permitting the detent d to engage with and hold one of the spars of pw. 

FIG. 319. 




When however the electro-magnet is closed for an instant it results that the 
detent d is withdrawn from the spur. The printing wheel pw at once starts to rotate, 
but before it can move far the electro-magnet em is again demagnetized, and the de- 
tent D resumes its former position and engages with the next spur. Consequently, aa 
there are but six spurs, at equal distances apart, the opening of the electro-maofnet 
has only permitted the printing wheel to make the one-sixth of a revolution. But, in 
making this portion of a revolution the printing wheel has performed four important 
functions, namely: It has operated the lever k, which has stopped the rotation of 
the type-wheel tw; it has operated the lever PL,which has printed the desired letter. 
It has, by operating mechanism, shown in Fig. 319, advanced the paper tape a suitable 
distance, and it has again operated the lever r, causing it to withdraw the detent d 
from the teeth of st, permitting the type-wheel tw to resume its motion. 

At rest, as in the figure, the angular arm at the end of lever e is nearly in con- 
tact with the pin p' on spur s^ of pw. When pw begins to move, this pin engages 
with the arm of e and pushes the detent </ between the teeth of st. The pin p' 
then continues to glide along the curved edge of R still holding it so that detent d 
remains between the teeth of st, until the next spur Sg arrives nearly at the position 
just held by s', when the projection a 2 on Sg engages with the inclined end of e, 
pushing it towards the pin Pg, and, at the same time, withdrawing the detent d from 
between the teeth of st, which at once permits the type-wheel to resume rotation. 



PHELPS MOTOR PRINTER. 427 

111 the meaiitime, and during the same motion of the wh^el pw, the pin v^ on the 
main body of pw has come in contact with an end of the lever pl, raising 
that end, and, consequently, depressing the other end e against the paper, thereby 
printing a letter: having done which the lever resumes its former position, its lower end 
then resting, on pin Vg, ready for the printing of another letter, at the next motion of 
the jjrinting wheel pw. It will be seen from the relative position of the lever r to 
the pins Pi,Po, etc., and the angular projection A,and that of lever pl to the pins v^, 
V2, etc , that the type-wheel will be arrested before the lever pl can have reached the 
paper, and that, further, the latter lev^^r will have arisen from the paper before the 
detent d of the lever k has been withdrawn from the teeth of st. 

Phelps synchronizing device. — In the '' stej^ by step" printing telegraph sys- 
tems we have seen that the rotation of the receiving apparatus is controlled by the 
transmitter and that the rate of rotation of the receiver is thus made to conform 
to that of the transmitting apparatus. In the Phelps system, however, such is not 
the case, the transmitter and the receiver being practically independent of each other, 
so far as the operation of the latter by the former is concerned. 

It is therefore obvious that some means must be employed to secure synchronism 
between the Phelps transmitter and receiver. 

The device by means of which tlie Phelps system is synchronized consists of the 
detent ^attached to lever e, Fig. 318, which is caused to perform a double function, 
one of which has already been described (namely the arresting of the type- wheel). 
It performs its synchronizing function as follows: The shape of the detent is such that 
it fills the space between any two teeth, when it is placed therein. Hence, if the 
toothed wheel st should be slightly in advance of the transmitting wheel h. Fig. 313, 
the detent d^ which is actuated })rimarily by that wheel, cannot fully occupy the space 
between any two teeth except by pushing back wlieel st, and with it, of course, the 
type-Avheel. Contrariwise if wheel st should have lagged slightly the detent d will 
push it the necessary distance forward. Inasmuch as this action is repeated at the 
printing of each letter, a considerable variation from actual synchronism in the revo- 
lution of the receiving and transmitting apparatus might take place before the instru- 
ment will *' throw-out." Perhaps, this synchronizing action will be clearer to some if 
it is pointed out that it embodies the now well known clock synchronizing princij)le, 
in which the minute hand is pushed forward or backward if not keeping the correct 
time, by the action of the armature of an electro-magnet. The function of synchro- 
nizing the type-wheel, or,as it is called, correcting the synchronism of that wheel, 
may, therefore, fairly be added to the other functions specified of the printing wheel 
of the receiving apparatus. 

Unison Device. — The mechanism of this system by which the type-wheel is 
brought to unison, is shown in Fig. 319. 

In brief, the unison device may be said to consist of means whereby the type- 
wheel is brought to rest at a certain point after a few revolutions, when the printing 
wheel is not iji operation, and of additional means whereby the action of the device 
which would thus bring the type-wheel to rest, is prevented from acting upon that 
wheel so long as the printing wheel is in operation. In the figure, tw is the type- 
wheel. (This wheel has 26 letters and one blank space on its periphery.) cw is a 



428 AMERICAN TELEGRAPHY. 

small cog wheel, or pinion, on the same shaft asTW. uw is a toothed wheel, meshed 
with cw. The shaft s, on which wheel uw is mounted, extends beyond the wheel, w is 
a cm'ved rod pivoted on an end of arm i of a 3-arm lever l, which is pivoted at x. 
The left end of w rests on the shaft s and it is caused to rest snugly against the shaft 
by the pull of a spring rs. Consequently, when the type-wheel and the wheel uw are 
rotating, the latter in the direction shown by the arrow, the rod w is given a gradual 
upward movement. This movement of w turns the lever l on its axis and, if nothin^f 
prevents this forward motion of the rod w^ the arm 3 of the lever l will; after a few 
revolutions of tw, be interposed in the path of a pin p projecting from the side of the 
type-wheel. 

When this occurs, as shown in the figure, the type-wheel . is held fast, with the 
blank space on its j^eriphcry opposite the pad of the printing lever pl, Fig. 318. 

It will be seen, however, that the arm 3 of l is now directly in the path of pin P5 
on a spur of the printing wheel pav. Hence, at the moment a distant key is depressed 
and the detent, on the armature lever of em. Fig. 318, is withdrawn, the pin ps 
throws arm 3 of lever l out of its i3ath, which instantly throws arm 2, of l, out of the 
path of i)ln p on tw^ thus permitting the latter wheel to rotate. Inasmuch as, in the 
act of printing the letters, the printing wheel is kept in almost continual motion, it will 
be evident that the arm 3 of lever l will be constantly set back by contact with the 
pins on the spurs of that wheel andj consequently, the arm 2 cannot, while the printing 
operation is in progress, get into the path of the pin on the side of the type-wheel. 

When the type-wheel has been brought to unison it is necessary that the trans- 
mitting operator should depress his " blank " key before proceeding with his message. 
This starts the type -wheel at once and as the " blank " key corresponds in position with 
the blank space on the type-Avheel, which is below the printing platen at that time, the 
transmitting apparatus and the receiving apparatus will rotate with corresponding 
letters in, as it were, proper alignment. 

Paper Feeding Mechanism : — The paper feeding apparatus of this system, which 
is also shown in Fig. 319, is virtually similar to that of the Phelps stock printing 
instrument. In the operation of this apparatus the small pins r r on the printing 
wheel pw, and the notches 11 n in the wheel nw, are utilized. The wheel roller mw 
and the wheel nw are on a common shaft /. jr is a smaller roller, supported by a 
flexible rod r', and resting lightly on the paper strip pt vvhich passes between jr and 
MW. Normally, one of the pins, r, is in one of the notches n, of wheel nw. When the 
wheel Pw is allowed to move the distance between any two of tlie spaces, the pin r 
engages with the edge of the notch and pushes the wheel Nw.a short distance out of its 
path. As the wheel nw is turned the paper tape is urged a short distance to the left. 
The pin then leaves the notch, and the next pin moves into the next notch, ready to 
give the wheel nw a further turn at the next movement of pw. Thus, at each partial 
revolution of pw,the paper is moved a certain distance, sufficient to properly separate 
the letters, and the arrangement of the printing lever pl, Fig. 318, is such that the 
printing is not done until the advance movement of the paper tape has been effected. 

It will be understood that the parts of the receiver shown separately in Figs. 318, 
319, are suitably placed on a common base to permit the necessary co-operation 
between them. 



PHELPS MOTOR PRINTER, 



429 



Adjustment, etc.— The motors of this system are adjusted in the following 
manner: The distant station depresses the blank, or space key (sp, Fig. 312). At the 
same time the home station permits his motor to ran. 

If the instruments are in synchronism nothing will be printed. If the letter a, or a 
B c should be printed, it shows that the home instrument is running too fast and the 
handle h, Fig. 313, of the governing apparatus, is raised. This permits the lever f to 
recede further from the disc wheel and thus slackens up the speed of the motor. If, 
on the contrary, the letters x y z, should be printed, it is evidence that the home motor 
is lagging, and the speed is increased by the pressure of the lever F on fd by which ac- 
tion more current passes through the coils of the motor. 

FIG. 320. 




CONNECTIONS OF PHELPS MOTOR PRINTER. 

To secure a space between words on the paper tape, the sending operator depresses 
the blank key between each word. This operates all of the printing mechanism at 
the distant end and moves the paper forward, but, as the blank space on the periphery 
of the type-wheel is opposite the platen at that moment, nothing is printed. 

This system, is now worked exclusively on a quadruplex circuit. The polar side of 
the quadruplex is utilized solely for the transmission of messages, each way. The 
*' second," or neutral side, for "breaks " By this arrangement but one sending oper- 
ator is interrupted ; each receiving operator doing his own breaking. 

A diagram of the connections as arranged for quadruplex working is given in 
Fig. 320. 

The circuit breaking apparatus of the Phelps motor printer is shoAvn at a. 
Owing to the tendency to sparking at its contact points when applied directly to a quad- 
ruplex it is caused to operate a pole-changer PC, as shown, t is the transmitter, nr the 
neutral relay and pr the polar relay of the qradruplex. The polarized relay controls 
the printing magnet em. Breaks are sent by operating the transmitter which causes 
the sounder s in the local circuit of the neutral relav to o-ive a "break'' sio-nal. 



430 



AMERICAN TELEGRAPHY. 



The Essick Page and Line Printer. 



The printing telegraph systems thus far described have all used a paper fillet- or 
strip, on which to print the letters and figures. 

FIG. 321. 

Line. 




ESSICK PAGE AND LINE PRINTER, THEORY. 

The Essick " Page and Line " printer, as the name implies, departs from this 
method and furnishes a record of messages received on a page of paper. 



THE ESSICK PRINTER. 43 1 

This necessitates, of course, means for moving either the paper, or the type- wheel, 
suitable distances, laterally, as each letter is printed, and also means for moving the 
paper upward or forward a suitable distance at the end of each line. In the Essick 
printer it is the paper that is moved laterally and upward, and the type-wheel is held 
in a given position where it rotates on its shaft in the usual way. 

In addition to the special apparatus entailed by the page and line feature of the 
Essick printer, the transmitting and receiving devices of this system differ from any 
of the systems thus far described; in several respects quite materially. 

The Essick printing telegraph system is intended to be used either as a local or 
long distance printer. 

The theory of the transmitting and receiving apparatus is illustrated in Fig. 321. 
Tis the transmitter, R is the receiver at one station. Each terminal is, of course, simi- 
larly equipped. The transmitting cylinder c and the type-wheel shaft are rotated 
by spring motors with which they are connected by clock work gearing. The speed 
of rotation is governed by escape wheels ew, ew', and polarized relays pr, pr'. 

Reversals of polarity are used to effect the rotation of the polarized relays. These 
reversals are produced by a pole-changer Pc, under control of an escape wheel ew on 
the riglit end of the cylinder c of the transmitter. Ordinarily the rotation of escape 
wheels is governed by the escapements, as in the case, for example, of ew, ew? This 
procedure is reversed in the case of the escape wheel ew and the escapement e, 
(which latter is attached to what corresponds to the lever of the ordinary duplex 
pole-changer,) that escape- wheel actuatnig its escapement, thereby producing a motion 
of the levers of the pole-changer which rapidly reverses the battery mb. These "re- 
versals/' in turn, pass through the polarized relay pr, in consequence of which a mu- 
tually governing action, as between the pole-changer and the cylinder c, is secured; 
and by which also serious interruptions on the line wire immediately serve, either to 
hold the cylinder shaft, or to indicate to the attendant the presence of "trouble" on 
the wire. 

The rotation of the cylinder c is, itself, controlled by the keys of the key-board 
in a manner practically similar to that of cylinders of the same type already described ; but 
the actual construction and some of the details of the key-board of the Essick trans- 
mitter differ from the others referred to. These features will be explained separatelvo 

The type- wheel shaft s of the receiver p. is controlled by a local polarized relay 
PR, which is operated by reversals of polarity of the split battery sb; the said re- 
versals being caused by the armature a of the main line polarized relay pr'. As the 
latter relay is under control of the distant transmitter it follows that the reversals of 
polarity controlling the receiver will correspond with those caused by the transmitter. 

The press magnet pm of the receiver is in a branch circuit with the polarized relay 
pr. Owing to the rapidity of the pulsations this press magnet is normally open, but 
on the cessation of reversals its lever is immediately attracted. This magnet doc'^ 
not effect the printing directly, but it releases mechanism which does. The same 
mechanism, wnen thus released, also acts to move the paper carriage, laterally, and to 
throw off the unison device, in a somewhat analogous manner to that oF the printing 
mechanism of the Phelps stock printer. 



4: 



AMERICAN TELEGRAPHY. 



A front vicAV of the paper carnage of the receiver is shown in Fig. 322. The 
frame of the carriage is indicated by//. The frame is carried and guided by wheels 
w w w. The rack-bar r is also carried by the frame. An endless screw w rests nor- 
mally in the teeth of the rack. ^Y is mounted rigidly on the shaft A. At its right the 
same shaft supports a pinion /; which is geared with a large cog wheel cw, A pin 
r projects from the right end of shaft a. This pin is normally held by the upper tine 
of a double detent ^, Fig. 323, carried by the lever l of the press-magnet. When the 
armature of lever l is attracted the pin r is released. This permits shaft a to make one 
revolution, at the end of which revolution the pin r is held by the lower tine of detent d, 
until the armature again rises, when the pin r is again held by the upper tine of ^. The 
act of turning the shaft a once, moves the carriage laterally a distance equivalent to 
the width of one letter of the type-wheel, against the pull of a recoil spring contained 
within the pulley p. The left end of the shaft a rests in a movable bearing b. This 

riG. 322 




Ov 



J 



ESSICK PAPER CARRIAGE, FRONT VCEW. 

bearing may be raised or lowered by shaft x. When this shaft x is oscillated, as at 
certain times it is, it operates an eccentric /which raises the endless screw w out of 
til e rack; thereby allowing the rc^.oil spring to withdraw the carriage to the starting 
point. 

When the carriage has been moved forward to the extreme left a small bell is 
automatically sounded, as an indication thereof; whereupon the operator depresses a 
key wliicli allows the escape wheel ew' of the receiver to run continously for a few 
revolutions, which action brings into play a device, to be shown subsequently, that 
lifts the endless screw out of the rack. It is not necessary, however, that the carriage 
should be moved to the extreme left before bringing this mechanism into play; it may 
be returned, in the same way, to the starting point at any part of its trip. 

The device whereby the paper is moved upwards at the end of a line, is indi- 
cated in Fig. 322, at rw' and a' . a' is an arm set out at an angle from the frame, 
and forming, with the frame^ a horizontal v. The vertical rod, or lever, Q, is pivoted 



THE ESSICK PRINTER. 



^33 



at X on the frame of the carriage. This rod, q, carries a pawl ^' which rides on a 
small ratchet wheel riu. On the same shaft with rw is a roller rw^ the upper edge of 
which is seen. Opposite rzo' is a roller k, suitably pivoted, which presses against the 
paper. The act of pushing forward the rod causes the pawl d' to engage with its 
ratchet wheel and thus rotates the rollers. In returning, the pawl simply slips past 
the teeth on rw. A suitable spring holds the rod q out from the upper part of the 

FIG. 323. 




ESSICK PAGE AND LINE RECEIVER — THEORY PRINTING DEVICES. 

frame a certain distance. Thus when the carriage is being returned to the starting 
point the rod impinges against the arm a' and is quickly pushed forward, thereby 
causing the pawl d' to turn the rollers, which eifects the desired upward movement 
of the paper. The paper is outlined at the bottom of the carriage frame. 

A side view of the principal actuating parts of the printing and carriage-moving 
mechanism, just referred to, is given in Fig. 323. 

In this figure pm is the press magnet, l is its lever extending to the double de- 
tent^, cw is the large cog-wheel which imparts the rotary motion to the shaft a, 
and with which the pinion/ on shaft a is geared. Shaft a also carries an eccentric, 
or cam, c. Opposite c is placed an extension e^ mounted rigidly on a shaft m m 
also carries extensions e and Eg. e is placed directly behind the type- wheel tw. The 
shaft x which carries the eccentric / also carries at its left end the depending arm 
n. The arm rmof the lever /, at its lower end is slotted, as shown, and a pin project- 
ing from the arm ;z, fits in the slot. Another bent projection /f from /rests, normally, on a 



434 AMERICAN TELEGRAPHY. 

pill,/'', on the side of extension e^. The left end of lever /is provided with a short 
rack rx which, normally, rests in the pinion k. This pinion is in constant rotation 
when the receiver is in operation. Consequently, if the rack rx were allowed to rest 
continuously in the teeth of k, it would be quickly drawn to its limits, against the 
pressure of the tension spring st. This act would push the extension n to the left, 
thereby oscillating shaft x and causing the eccentric /, Figs. 322 and 323, to lift the 
endless screw w out of the rack e, for the purpose stated. 

As long, however, as the rack rx of lever / is prevented from resting continuously 
in the teeth of k, the oscillatory movement of shaft x does not take place; and as it 
is imperative that this action should only take place at desired intervals, a device 
analogous Co that used in printing telegraph systems for preventing the action of the 
"unison " device during the regular printing operation, is employed. 

This device consists of the bent arm ^, attached to /, which operates to insure 
the desired effect as follows; 

At every downward motion of the armature of the press magnet we have seen 
that the shaft a is permitted to make one revolution. In making that revolution 
tJie cam c on that shaft strikes against the extension e'. This action oscillates the 
shaft M and, consequently, the extensions e^ and Eg with it- Thus, at every stroke of 
the cam c the extension Eg by means of pin p^, is caused to lift the rack rx of lever / 
out of the teeth on the pinion k^ thus preventing it from oscillating shaft x. 

The unison device is shown in Fig. 323. . It consists of the endless screw w of 
the type-wheel shaft and the pins u and u'. The operation of this device is practi- 
cally similar to others already described. N'ormally the pin ii' would rest in the . 
thread of the endless screw w. The rotation of the type-wheel shaft would bring the 
]»in u' into a position where it would engage with the pin u^ thus stopping the type- 
wheel at a certain point, that is, with the "space," or dot, opposite the hammer h' . In 
the operation of the printing mechanism, however, the pin it' is continually lifted out 
of the screw threads and brought back to its starting point by the pull of the spring s. 

The office of the projection n' from the strip m is to insure the operation of the 
rack rx when desired. For instance, it was found that sometimes the rack rx would 
rest on the top of the teeth k before meshing, for a sufficient time to permit the 
type- wheel to come quickly to unison, thereby preventing the desired return of the 
carriage to its starting point. The projection n' is so placed that it holds the unison 
pin It' out of the screw threads until the rack meshes with the pinion teeth. 

It will be understood that the press-magnet is only operated when it is desired to 
print a letter, or to effect a motion of the carriage for spacing. Since then the exten- 
sion E from shaft m is urged forward, at each motion of the press-magnet, by the 
actioi., of the cam c, it will be seen, the hammer h' attached to the lower end of e 
will strike against the type-wheel, or rather the intervening paper, and impress thereon 
the letter desired to be printed. 

It is thus obvious that the various actions of the printing and moving mechanism 
are, almost entirely, mechanically performed, the press-magnet merely serving to set 
free the mechanism at the desired instant, the result of this release' being to permit 
the rotation of shaft a, by which act the carriage is moved laterally , the unison device 



'HE ESSICK PRINTER. 



^35 



is held out of contact with the pin u, the lever / is prevented from operating eccentrits 
y, and the printing is effected. 



FIG. 324. 



i! !'"',!"l 




ESSICK PRINTER, KEV-BOARD AND TRANSMITTER. 



The transmitter and key-board are shown, top view, Fig. 324. s s are switches 
whereby the necessary cnange from '^ sending " to "receiving" is effected. PC 
is the pole-changer, c the " pin " cylinder. Each key on the key-board is provided, 
as shown, with a lever extending to the cylinder ; which lever is furnished with a de- 
tent, (outlined in side view of the transmitter, Fig. 325,) by means of which it ei> 
gages with its corresponding pin on the cylinder. 

A device, whereby any key depressed is held down until another key is depressed 
is shown also in Fig. 325. It consists of the bent lever /^, which carries a rod r 
(shown in cross section in the figure) placed at the lower ends of the key lovei-s, as 



436 



AMERICAN TELEGRAPHY. 



outlined in Fig. 324. The rod r is cut away on its under side, so that, when a lever is 
depressed, its end passes under the rod and is held there until the depression of the 

FIG. 325. 




i 



next key lever pushes the rod back, allowing the first lever to rise. iTiis device, if 
^ot desired may be readily dispensed with by holding it out of the path of the levers. 



FIG. 325^'. 



EXCHANGE ....BR PR 



KIN 



486.488 39 



80 



11.14 



In Fig. 325^, specimen of printed slip as received by a tvro type-wheel ticker, is 
shown in fac-simile. The initials on top lines stand for the name of the stock; the 
figui-es on lower lines, for the market quotations. 



The Hughes Prixter. — This printer is quite largely used in Europe, and to 
a limited extent in Great Britain. The Phelps Motor Printer described herein 
embodies the essential features of the Hughes, and may be considered an improve- 
ment thereupon, especially as regards rate of signaling, which by the Hughes sys- 
tem is 30 to 35 words per minute, the message being received on a paper tape. The 
Hughes relay, described on page 240c, is employed as the main-line relay of the 
Hughes printer. Up to a recent period the mechanism of this printer was spring - 
driven, but an electric motor analogous to that of the Phelps is being applied to 
the Hughes system. 



buckingham printer. 436^ 

The Buckingham Automatic Long-Distance Page-Printing 

Telegraph. 

Ix the step-by-step and the synchronous printing telegraph systems already 
described, it is evident that a considerable loss of time ensues, from the fact that it 
is frequently necessary to rotate the type-wheel the greater part of a revolution in 
order to print one letter. Thus, if the letter A follows B in a given word, it will 
require 31 pulsations of current to print A. If H follows C, 15 pulsations will be 
necessary. This gives an average of about 15 pulsations for each letter, and for the 
space between words as well, and hence conduces to a low rate of speed, an average 
of perhaps 25 to 35 words per minute. In addition the message is printed as 
received on a paper strip, which is not an acceptable form for delivery to the 
public. When also it happens that the transmitting wheel, or cylinder, and a type- 
wheel on these step-by-step systems get out of unison, or throw out, it is necessary 
to let the transmitter run free for two or three revolutions, until a unison device is 
actuated, this often requiring 60 or more pulsations of current. In the case of the 
synchronous systems described it is frequently necessary to allow the apparatus to 
run free for several minutes to obtain unison. In the Phelps system, for instance, 
synchronism is obtained as follows : The sending-station regularly depresses a pre- 
arranged letter, for example, the letter A. If then the letter B is received, and 
subsequently the letter C, the receiver is running too fast. The speed is then 
reduced until the given letter is printed, and vice versa. It may also be noted in 
this relation that quite a high degree of skill is required on the part of the operator 
of tiie Phelps and similar keyboards to secure the best results. Probably for the 
foregoing reasons the use of the Phelps printer is gradually being discontinued in 
this country (1902). 

The Buckingham Long-Distance Pag^-Printer is the successful outcome of the 
work of the inventor, Mr. Charles L. Buckingham of New York, assisted by Mr. E. 
Germann, to produce a rapid page-printing telegraph system adapted to operate on 
the longest circuits, and to avoid the paper strip and other objectionable features of 
previous printing telegraph systems. 

It is evident that to attain these ends it was necessary to diminish largely the 
number of pulsations required for the transmission of letters and spaces below that 
requisite on the ordinary printing telegraph. As a first step in this direction the 
Buckingham printer employs 4 octagonal type-wheels, each less than one-half inch in 
diameter and one-eighth inch thick, fixedly mounted on one shaft side by side. On 
the periphery of each wheel are placed 8 letters and other characters, 32 in all. The 
shaft on which this combined type-wheel is mounted is so disposed that by an inge- 
nious arrangement of 5 arms or levers attached to the shaft the type-wheel may be 
given a lateral or rotary motion, such that any one of the 32 characters on its per- 
iphery may be placed before a given point for printing, by 5 pulsations of current, 
that is, two and one-half alternations of polarity, from the transmitting-station. It 
may also be noted here that the Buckingham receiving-apparatus is so arranged that 
a succession of short pulsations must always bring the escape-wheel of the receiving- 
apparatus, and with it the type-wheel, to the zero or unison position and lock it 
there, in a manner to be explained subsequently. For the actual printing of the 



436^ 



AMERICAN TELEGRAPHY. 



letter, in the Buckingham system, the interval corresponding to the space hetween 
letters and words in the Morse and Wheatstoiie systems is utilized. Hence the selec- 
tion and printing of any chai-acter is brought about by a cycle of 6 pulses of 
current in all that is to sav, 3 reversals of polarity. These pulses are, however, of 
varying lengths, akin in this respect to the Morse alphabet. For example, the letter 
A will be selected by a dash and two dots. B, by a dot, space, dash, space, dot; the 
space, as in the Wheatstone system, being made by a negative current, and, since it 
is known that a succession of 5 short and long pulses can be arranged in 32 different 
ways, a different combination is readily obtained for the 26 letters of the English 
alphabet and 6 other characters. 

These combinations form what is termed the Buckingham alphabet or code, 
given herewith : 



aI.. 


1 


I Q... . 


. ... y ... . . 


B - 


: J = ..i 


u, R . .,. 


■ z 


Q n > 1 


« K 4 4 


"" s 


& 


D .. . 


■ l] "■ 


1 1 1 1 I 


/ 


E 


M|' - 


.. u . 1 


' 


p,... 


. fy. ... 


■ V 


' ? 

■ 


c ■ . 


11 ■ ■ ■ 


y... . 


"II ^ 


Hm\ 


M PH iH 


11 XH U 


4l Space nMH 



BUCKINGHAM ALPHABET. 



Inasmuch as the prolonged negative or positive pulse of this aljDhabet, like that 
ot the Morse dash, is theoretically equal to three short pulses, that is, as the dash is to 
the dot, the letters of the English alphabet that are known to occur most frequently 
in the English language, are, in the Buckingham alphabet, allotted the combinations 
which contain the least number of prolonged imjjulses. The figures in this system 
are transmitted by the use of the Eoman numerals, as in the case of the Phelps 
sj^stem. 

In the feature of preparing the messages for transmission, and in the actual 
transmission of the messages, the Buckingham system is almost identical with the 
Wheatstone automatic system. Consequently, the messages are prepared for trans- 
mission by being perforated in a double row on a paper strip, which is then passed 
through the Wheatstone transmitter, and if the Wheatstone receiver were employed at 



BUCKINGHAM PERFORATOR. 436^ 

the receiving-end the messages would be recorded on the paper strip as dots, dashes, 
and spaces, differing from the Wheatstone records only as the Buckingham alphabet 
diHers from the Moi"se alphabet. 

The transmission of the six pulses of alternating polarity thus arbitrarily arranged 
for each character results in the operation of a Wheatstone polarized relay in the 
main line at the receiving-end of the system, which relay by its armature controls 
local circuits in which are a governing-relay, a unison-magnet, and an escapement- 
magnet, which latter imparts, by means of an escapement, a step-by-step motion to 
a "sunllower," or distributor, of peculiar construction, to such purpose that, with 
the co-operation of the governing-relay, and depending on the duration of the incom- 
ing puUes and the order of their arrival, one or more selecting-relays are operated, 
and these in turn, by actuating certain type-magnets, cause tlie operation of the 
type-whecl-moving levers, which bring a desired letter on the type-wheel to the 
printing position. 

The Buckingham printer is thus a positive or " step-by-step " system, in which 
an escape-wheel, and with it the sunflower, or distributor, is caused by a cycle of six 
l)ulses of current, one or more of which is prolonged, to undergo a cycle of six steps 
for each letter or other character printed. Theteim " prolonged pulse " is a relative 
one, as will be unders-tood if it is considered that when the system is operating at the 
rate of 100 words per minute the length of a prolonged pulse is about the one- 
fortieth of a second. 

Before considering the receiving-apparatus further, the manner of preparing 
messages for transmission by the Buckingham system will be described. 

As already noted, the ordinary method of preparing messages for transmission by 
the Wheatstone system is a somewhat tedious and arduous process. The rate at 
which a Wheatstone puncher can prepare messages by the mallet method (page 297) 
is from 20 to 40 words per minute. One of the important features of the Buckingham 
system is that it dispenses with this mallet method of preparing messages, in which 
every element of a letter has to be punched separately by the operator, and instead it 
employs a method in which all the elements of a given letter, and the space between 
letters, are perforated by the depression of one key on a keyboard corresponding to 
that of the Kemington, and by means of which messages can be prepared for trans- 
mission by the Buckingham system at a maximum speed of about 80 words per 
minute. The keyboard of this perforator is outlined in Fig. 325^, and its operation 
may be described as follows: Under and at right angles to the levers K of the kevs a 
number of fine piano- wires, li li^ are stretched at intervals of about .25 inch. These 
wires are fixed at the left end, while at the right end each wire is attached to a 
separate crank-lever contact o, which controls a circuit in which is an electromagnet. 
There are in all 24 of these wires, 15 of which, through their crank-levers, control 
an equal number of punching-magnets, and 9 of which control 9 paper feed-magnets. 
The key-levers are provided with inverted stirrups on their under edges (the actual 
number and position of which are different for each key or letter), and when a given 
key-lever is depressed these stirrups engage with certain of the piano-wires, which 
latter operate the crank-lev^'s with which they are connected^ and thereby close the 
circuits of their respective electromagnets. 



436^ 



AMERICAN TELEGRAPHY. 



The punch- and feed-magnets and their circuits are shown diagram matically in 
'Fig. 325^. o' indicates the actual type of crank-lever operated by the piano-wire. 
For simplicity the remainder of the crank-levers are represented as at 0. Tliey 
are pivoted as shown at ^ ^ on the same metallic base m. Their lower contact points 
are indicated by I. The 16 punch-magnets are represented by letters b; the 9 feed- 
magnets by H. b' b' are two magnets termed "assist" magnets, which are em- 
ployed to assist in withdrawing the punches after the paper has been perforated, in a 

FIG. 325(2. 



Tffii [iOi]?i V"'n """ 




BUCKINGHAM KEYBOARD PERFORATOR. 



way shortly to be explained, i is a magnet termed the "knock-down" magnet, the 
use of which will be described in connection with the paper feed-wheel of the per- 
forator. It is controlled by the circuit-closer ^^, which is carried on the armature- 
lever of an assist-magnet b', as shown on the left side of Fig. 325c. Normally the 
circuit of magnet i is open, but when the assist-magnets are attracted it is closed. 
By suitably adjusting i i the action of i may be hastened or delayed. Inasmuch as 
every letter of the Buckingham alphabet begins with a positive pulse, the magnet 
which punches the first hole of each letter is always operated without the need of a 



BUCKINGHAM PERFORATOR. 



436^ 



piaiio-wire. This magnet is shown as b at the right top corner of the figure. This 
explains why 24 piano- wires suffice for 25 magnets. The circuit- closer qq' \^^ com- 
mon closing point for all the other contact points. It is operated by all of the keys 
of the keyboard by means of a horizontal bar, shown in preyious figure. It is so 
arranged that whenever any key is depressed it closes before a piano-wire can operate 
a crank-lever 0, and 

it is opened before ' fig. 325/^. 

the wire releases its 
crank-lever. In this 
Avay any sparking 
at the opening of 
the circuit occurs at 
the common con- 
tact point, Avhich is 
made of suitable 
material to with- 
stand such spark- 
ing. In Fig. 325^ 
the key of letter A 
is assumed to be de- 
pressed, with the 
result that all the 
contacts connecting 
with the proper 
punch- and feed- 
magnets for this let- 
ter are closed. The 
source of E. M. F. 
is indicated by a 
battery MB, but in 
practice a dynamo 
machine is utilized. 
The route of the cir- 
cuits may be readily 
followed by means 
of the figures i, 2, 
3, etc. 

A side view of 
the punching ap- 
paratus and punch- 
magnets is given in 

Fig. 325c. , The punches a in this perforator are 16 in number, of the same diameter 
as those used in the Wheatstone mallet perforator. They are arranged in two rows in 
a box or punch-head g g, S being arranged on one side of the box and 8 on the oppo- 
site side. Thus they punch the paper strip from the opposite sides; the right-hand 




THEORY OF KEYBOARD PERFORATOR. 



436/ 



AMERICAN TELEGRAPHY. 



series of punches making the necessary upper holes in the paper, the other series the 
lower holes, the latter series being set lower for that purpose. The paper strip is 
caused to pass in a small space between the punches. The punch-magnets are 
represented by b. They are compactly arranged in four vertical rows, two of which 
are seen in the figure. Behind each punch a there is placed a crank-lever d d 
(pivoted at s 6'), one for each punch. Pivotally attached, as shown, to each of the 
armature-levers of the magnets B, there is a narrow metal arm t, which has on its 
upper end a hook that fits over a curved portion of the crank-levers d d. Hence, 

FIG. 325c. 



I <.^^^ 




when a magnet is attracted, the hooked arm pulls down the lower end of its crank- 
lever d^ driving the punch opposite its upper end forward through the paper strips 
Thus when any given key is depressed it will close a certain six of the circuits 
containing punch-magnets, which in turn will operate the punches connected there- 
with, therebyperforating three upper and three lower holes in the exact order required 
for the transmission of the letter represented by the key so depressed. From what has 
been said it will be understood that these holes are differently arranged for each 
letter or other character, in order to bring about the variation in the duration of the 
six pulses for each letter. 



BUCKINGHAM PERFORATOR. 



436^ 



To prevent the cuttings or chips from the perforated paper clogging up the 
apparatus, a chute or conduit z is provided into Avhich the chips fall, their downward 
passage being facilitated by the jarring of the arms Y against suitably arranged pins 
while the punching is in progress. ' 

The assist-magnets b' b' are shown at the top of framework, one on each side 
of the punch-head, h h are two arms which extend at right angles from the upper end 
of the armature-lev^ers of the assist-magnets. This armature is not seen in the figure. 
There are in fact two such extension arms t from each assist-magnet, although but 
one can be seen in this side view. To the inner ends of each of these extension 
pieces h h two downwardly extending levers n are pivotally attached, as at r. These 
levers are mounted on a shaft s' near their center, and are connected at their lower 
ends by a cross-bar h'. There is also a small crank-lever on a sleeve-shaft which 
is mounted over the shaft s' . These small crank-levers are also connected at 
their lower ends by a cross-bar m. They are connected to levers n by the small 
retractile springs i' i'. AVhen the armatures on b' b' are attracted they put a ten- 
sion on the springs a' a\ and at the same time loosen the tension on the springs i' i'. 
Also at this time the downwardly extending levers n are rocked inwardly, thereby 
moving the cross-bars h' away from the tops of the crank-levers cld^ and concurrently 
the cross-bars m of the small crank-levers are moved away from a projecting block 
attached to the outward ends of the punches f/, thns giving crank-levers del and the 
punclies a clear path in which to perform their respective functions. When the 
punches have acted and the assist-magnets are released their armatures are with- 
drawn, with the result that the cross-bars h' engage with the upper arm of crank- 
levers dd and return them to normal position. Also the cross-bars m on the small 
crank-levers engage with the projecting block on the punches, and the latter are 
withdrawn from the paper. 

The Perforator Paper Feed. — In the Wheatstone punching device the 
small central holes are punched simultaneously with the other perforations. In the 
Buckingham the central holes are prepared in advance by a special machine at a high 
rate of speed. The device for this purpose is shown in Fig. 32 5(;7, in which L is a 
reel holding the uncut paper strip, and B is a wheel having small cutting-pins D on 
its periphery. Under this wheel is a smaller one h, which has holes or dies set in 
its periphery in which the pins on B mesh. B is rotated by an electric motor as 
indicated. The paper strip is suitably guided through a chute between h and b, and 
is wound on the receiving-reel M, the speed of which is automatically regulated by 
the loose-fitting belt N, the operation of which is easily understood. An endless 
metal strip or band F with a continuous row of central holes corresponding to the 
pins on wheel B is placed loosely over wheel H and on the idler-wheels G. As the 
paper strip K passes between wheel b and the endless band, the cutting-pins perforate 
the central holes in the paper. The wheel B is operated at the rate of about 80 
revolutions per minute, and as it has 150 cutting- pins on its periphery, 12,000 or 
more central holes may be cut per minute. 

In the Wheatstone perforated strip, and also in the Buckingham strip, there 
are 10 central holes to the inch. If the upper and lower holes as well as the spaces 
between holes in space letters are termed "time units," and the '"dot" is taken as 



436/2 



AMERICAN TELEGRAPHY. 



the unit, then the short space between the elements of a letter will consnme, or 
occupy, I time unit; the dash wilJ equal 3 time units; the long s|)ace in letters will 
equal 3 time units; the space between letters will equal 3 time units; and the space 
between words will equal 5 time units. It is then easily calculated how much space 
on the paper strip must be allowed for a given letter, and consequently the amount 
of paper that must be fed for each letter. As already intimated, the first pulse of a 
letter in this and the Wheatstone systems is always of positive polarity; the last, of 
negative polarity. In both systems this last pulse does not count in the letter itself, 

FIG. 325a'. 




-CENTRAL-HOLE CUTTER. 

inasmuch as it performs an act exactly equivalent to that of the Morse operator's 
fingers when he withdraws them at the end of a letter. Obviously, at the end of a 
letter or word the key must be restored to normal, and the time so occupied counts 
in the Buckingham alphabet as one of the three time units between letters and words, 
during which the printing of the letter is effected. In the Buckingham system the 
paper is fed the distance required for the letter, and also by the one operation the 
distance of the space between letters. Thus, in Fig. 325^ it is seen that to letter A 
5 central holes are allotted (or, in the actual strip, .5 inch), which are equal to 10 

FIG, 325^. 



i ^ 




b 


c 


Xine 

jiiark. 


; CL i 


b 


: C , 

1 t 


lo 00 

<0 © 

j 000 



e 






0000 
00 


00 

c 
00 


ooc 

c 
000 


lo« 00e'0»0«0 
o|o 000 o|o 0000c 

;*ooo«o««oo 


[0 00 j 
[00000 010 

1 00 ! 


1 


— 





— 


1 


: 1- 





I 1 



time units (7 for the letter A and 3 for the space between letters). For the letters 
B and C, 6 central holes are required, or 12 time units (9 for the letters and 3 for the 
letter space). These time units may be counted on the right half of Fig. 325^, if 
the large holes and the black dots are each counted as one time unit. The length of a. 
time unit of course varies with the speed of transmission, but the number of time 
units in a given character does not vary. The line-mark which is made by the key- 
board operator at the end of each line by the depression of a key is also indicated in 
this figure. 



BUCKINGHAM PERFORATOR. 



436? 



There are six different lengths of characters in the Buckingham alphabet, 
hence the amount of i)aper fed varies with different letters. The variable feed 
action is antomatically performed in this perforator in a simple manner. The 
device for the purpose is outlined in Figs. 325/, 325^. It consists of a drum- 
shaped wheel 1.6 inch in diameter, on the periphery of which are placed small 
teetii d of the proper size, and so placed as to mesh into the central holes of the 
perforated strip. This wheel is carried on a vertical shaft d', frictionally driven 
by a motor-wound spring d. Fig. 325/, from which it may be manually discon- 
nected by raising it from the clutch e, a suitable lifting device being provided 
for that purpose. 

FIG. 325/. 




THEORY OF FEED-WHEKL PERFORATOR. 



There are arranged vertically around the edge of the feed-wheel a number of 
movable pins F, frictionally held in any position by the close-fitting spiral springs 
shown. These pins normally project below, but may be raised above the upper 
surface of the feed- wheel by lever /pivoted on post n\ f extending from the arma- 
ture-lever a of a feed-magnet. Lever/ is withdrawn by spring /'; p is a stop for 
the lever. Normally some one of the movable pins d is always raised as at the left 
of Fig. 325^, and while so raised it engages with a fixed stop c placed above the 
wheel, Avhereby the wheel's rotation is stopped. When a key of the keyboard is 
depressed, one of the feed-magnets referred to is operated, and through its connect- 
ing-lever / it drives up another of the movable pins as shown, which pin is distant 
from the fixed stop a space equal to the length of the letter represented by the key 
so depressed, together, as stated, with the letter space. Simultaneously with the 
raising of this latter pin, the proper punch-magnets have also been actuated and 
have punched the paper strip. At nearly the same instant the hammer end h of 
the armature-lever of the knock-down maguet i. Fig. 325^, has been placed above 
that pin which is now raised at the fixed stop c. When the operator removes his 



436/' 



AMERICAN TELEGRAPHY. 



fiDger from the key, allowing it to ascend, the circuits of the punch-magnets, feed- 
magnets, and assist-magnets are opened, the punches are withdrawn from the paper, 
and nearly simultaneously the hammer of the knock-down magnet hits the pin 
under it, depressing it below the fixed stop, whereupon the feed-wheel quickly turns 
until the pin last raised arrives at the fixed stop, when the wheel is again halted, and 
the apparatus is ready for the punching of another letter. Suitably arranged metal 
guides bring the movable pins into exact alignment before they reach the levers /. 
When the punched paper strip passes the feed- wheel it enters a curved chute, which 
strips it from the teeth of the feed-wheel, and it is then " run" through the Wheat- 
stone transmitter. 

In the operation of this keyboard perforator the operator depresses the keys pre- 
cisely as in the case of the ordinary typewriter, depressing a space key once for the 

space between w^ords. To pre- 
FiG. 325^ . vent the operator overrun- 

niug a line in preparing mes- 
sages for the Buckingham sys- 
tem, an escape-wheel, termed 
an indicator, is provided, which 
is rotated step by step with 
each key depressed. At the 
zero point of this wheel, which 
corresponds with the end of a 
line, there is a slot into which 
a pawl drops and locks the 
apparatus. To unlock it the 
operator depresses the line- 
space key, which at one oper- 
ation throws the pawl out of the slot and punches a line space. On the periphery 
of the indicator there is a white mark which comes into view as the end of a line is 
approached, giving the operator visual warning to that effect. When a message or 
any part of it ends in the middle of a line, the operator manually turns a knob on 
the axle of the indicator, which brings it at once to the zero or locked position, 
ready for the beginning of a new line, h is a device which insures the operation of 
the common break q in unison with the indicator. Fig. 325«. 

As intimated, all the business transmitted by the Buckingham system is pre- 
pared by this keyboard perforator, and it may be added that two thirds of all the 
business transmitted over the regular Wheatstone automatic circuits from the New 
York office has also been prepared by this keyboard perforator; it being understood 
that it is only a question of arranging the necessary combination of feed- and punch- 
magnets to adapt the keyboard to any dot-and-dash alphabet. Fig. 325a repre- 
sents a keyboard perforator arranged for the Morse alphabet and numerals, in which 
case no indicator is necessary. 

Details of Eeceivixg-Circuits and Appaeatus. — Details of the receiving- 
circuits and apparatus of this system are shown in Fig. 325//. The current for the 
operation of these circuits is furnished by a dynamo D. To simplify the diagram 




BUCKINGHAM PERFORATOR. 436>^ 

the circuits are shown as having ground returns, the negative pole of the dynamo 
being indicated by the minus mark and the conventional symbol of an earth con- 
nection. In fact, metallic circuits are employed. M L is the main-line polarized 
relay. Its armature controls two branch circuits c c' (fed by dynamo d), in which 
are a polarized escapement-magnet E M, a unison-magnet u M, and a governing-relay 
G R of the neutral type. These each have two coils reversely wound as indicated. 
In the case of the escapement-magnet the effect of a current alternating in the coils 
is to oscillate its armature from side to side in common with the armature of the 
main-line relay, this permitting the step-by-step movement of the escape-wheel E w. 
The unison-magnet is polarized and its coils are so connected that a current through 
oue of them corresponding to a negative current on the main line tends to assist the 
induced magnetism, while a current in the other coil (corresponding to a positive 
current on the main line) opposes the induced magnetism of the magnet. The 
adjustment of the armature-spring of this magnet is such that short pulsations of 
cither polarity will not attract the armature, neither will prolonged positive pulses 
attract it, but the armature will be attracted by prolonged negative currents, the 
result of which is that when short and long positive and short negative currents are 
being transmitted on the main line, the hook h on the end of the armature a of the 
unison-magnet is always in the path of, but between, the teeth of the unison- 
wheel u w, which latter is on the same shaft s as the escape-wheel E w; but when 
a long negative pulse is received, the armature of u M is attracted and the hook is 
withdrawn from the path of the teeth. There are 15 teeth on the unison- wheel and 
45 on the escape-wheel E w. 

The space between any 2 of the teeth on the unison-wheel is equal to the 
space between any 3 of the teeth on the escape-wheel. Six pulses of current will 
move the escape- wheel a distance of 3 teeth; therefore 6 pulses will also move the 
unison-wheel a distance equal to that between 2 of its teeth. Hence, so long as the 
unison- wheel is In^ proper step with the received pulses of a letter, the hook h will 
always be drawn out of the path of its teeth, since each letter of the Buckingham 
alphabet is followed by a long negative pulse; but whenever the apparatus gets out of 
unison 5 short pulses of either polarity will, as already stated, operate to hold the 
unison- wheel at the zero point, which is the point at which the apparatus is in the 
correct position to receive a new cycle of pulses. 

The teeth of the unison-wheel also perform another important office. There 
are six circuit-closing levers, indicated at k and pivoted and numbered as shown, of 
which levers five are on the one metallic support s; the sixth is on a separate metallic 
support s', insulated from s. These circuit-closers with the unison-wheel comprise 
the sunflower, or distributor, of this system. The arrangement of these levers relative 
to any seven of the teeth on u w, is such that when the unison-wheel moves a distance 
equal to the space between two of its teeth, these levers ride over one or other of the 
teeth, thereby closing their respective circuits at i, 2, 3, 4, 5, 6 in quick succession, 
beginning at i. In other words, each cycle of six pulses, whether of long or short 
duration, will bring about a brief consecutive closing of the circuit controlled by 
these levers, for a purpose presently to be mentioned. Of course a long pulse will 
cause a circuit-closer to dwell longer on its contact than a short pulse, and, as will 
be understood later, the sixth lever rests normally on a tooth. 



A-^^l 



AMERICAN TELEGRAPHY 









ij^^ 



BUCKINGHAM PRINTER. 436m 

Tlie armature-spring of the governing-relay G K is so adjusted that its armature 
will not respond to short pulses of current, but will respond to prolonged pulses of 
either polarity. This feature is utilized in connection with the circuit-closers of the 
sunflower, and certain polarized relays, termed selecting-relays s E, of which there 
are 5, numbered i, 2, 3, 4, 5, respectively. These relays also have two coils, al^^o 
reversely wound. One of the coils of each relay is connected to the correspondingly 
numbered contact post of the sunflower, but as the support s of these circuit-closers 
is connected to a contact point of the governing-relay, this circuit cannot be fnlly 
completed until the armature of that relay is attracted. The other coil of each 
selecting-relay is in series in a circuit r c, termed the restoring or resetting circuit. 
This circuit is controlled by the armature a' of a neutral relay termed the "throw- 
back " or restoring-relay R R, as will be explained more fully. The selecting-relays 
by their armature-levers control certain magnets, indicated at i, 2, 3, 4, 5 in 
Fig. 325/, which latter by their armatures mechanically move certain arms connected 
with the type-wheel-moving devices. Figs. 325?, 325/. These magnets are termed 
the type-wheel magnets, and by their aid any character on the type-wheel is brought 
to the printing position. 

Whenever, in the course of an incoming six pulses that represent a character, one 
or more of the pulses are prolonged, there will be a prolonged pulse or pulses in the 
circuit of the governing- relay G R which will attract its armature, as in Fig. 325/^. 
Assume, for example, it is the first pulse. At this moment circuit-closing lever i 
is on a tooth of the unison-wheel, and its circuit is closed at contact post i of the 
sunflower. Hence at this instant the selecting-circuit s c oi selecting-relay No. i is 
completed, and being thereby actuated by current from dynamo D, its armature 
is attracted to the right, closing the circuit of and operating type-magnet No, i, 
Figs. 325/, 325^. This magnet by its armature-lever will move the type- wheel into 
a position for printing the letter A, and if there be no other prolonged pulses in the 
cycle up to the sixth pulse, that letter will be printed. Had the third and fifth 
pulse of the cycle also been prolonged, the third and fifth selecting-relays would have 
been operated, with the result that letter K, and not A, would have been printed. 

The circuit-closing lever No. 6 is the last to act (it may be said to be the first 
and the last, for, as stated, it I'ests normally against its contact point, but it leaves 
it at practically the instant that circuit-closer No. i makes its contact). This lever, 
No. 6, when it closes, completes the circuit (from dynamo d) of two relays, one of 
which, the sixth-pulse relay s p, by its armature-lever closes the circuits of the press- 
magnet p M, the printer escape-magnet m', an ink-ril)bon magnet R r, and a dogging- 
magnet m ; the other is the restoring or resetting- relay R R, which closes the 
restoring-circuit r c, and thus resets the selecting-relays and type-magnets to normal 
position after the selection and printing of a letter, by means of the restoring- coils 
of those instruments. It need not be said that these operations follow each other 
very quickly. It is obvious that the apparatus actuated by relay s p must operate 
before the restoring-apparatus performs its part. This is insured by giving the 
armature-lever of relay R R a longer distance to travel before it makes its contact, 
and also by suitable adjustment of the springs of the armatures. The ink-ribbon 
feed-magnet R F actuates a step-by-step ratchet and pawl which moves the inking 



436n 



AMERICAN TELEGRAPHY. 



ribbon (not shown) so that a new surface is regularly brought under the type- wheel of 
the printer. The functions of the doggiug-magnet m, printer escape-magnet m', and 
press or printing magnet will be described subsequently. 

In series with each of the selectiiig-coils s a, and in series with the restoring- 
coils r c of the selecting-relays, Fig. 325/^, there are two coils of another relay, termed 
the non-print relay K p, the office of which will now be described. Being in series 
with each of the selecting-coils of those relays, the armature of N" p will be thrown to 
the right when any one or more of the armatures of the selecting-relays are thrown 
to the right. Tne armature of ]S" p will also be thrown to the left when the restoring- 
circuit is closed. It may be seen that the circuit of the press-magnet p M is led to 
the armature contacts of :^ p. The object of this is to avoid operating the press- 
magnet p M when the cycle of pulses representing the space between words is trans- 
mitted, the space cycle al>o being terminated by a long negative pulse, which of 
course will operate the sixth-pulse relay and restoring-relay, and therefore, normally, 
the press-magnet p M. As, however, during the space cycle none of the selecting- 
relays has been thrown to the right, the non-print relay is not actuated, and hence 
the press-magnet will not be operated, its circuit being open at the contacts of k p. 
Lest, however, the circuit of the press-magnet should tend to be opened at N p 
before it has finished printing, a branch or extra circuit is provided around the con- 
tacts at the armature of x p, by way of the tongue and contact point x y on the 
press-magnet lever, which, when the latter is once closed, keeps it so closed uniil 
the circuit is next opened at the sixth-pulse relay s P. The rod m is a manually 
operated device. In addition to other offices which it is caused to perform, and 
which will be mentioned further on, it closes and opens the circuits of the dogging- 
magnet m and the ink-ribbon feed R F (which are in multiple), at the spring con- 
tacts m' n respectivel}^ AVhen the rod is pulled to the right the contacts separate, 
and vice versa. The object of opening these circuits is to free the printer appa- 
ratus so that the paper blanks may be inserted or removed at will in a way to 
be described. 

The E. M. F. of dynamo D is no volts. The resistance of each coil of the select- 
ing-relays is 200 ohms. Sufficient extra resistance is inserted in the circuits at r r' 
to bring the current strength to about .055 amperes. Condensers are placed around 
contact points to reduce sparking when necessary; // represent the usual fuses. 
A differential galvanometer G, similar to that used in the Wheatstone automatic 
system, is employed to facilitate the adjustment of the armature-lever of M l, when 
required. The apparatus, however, needs but little adjustment, and it will operate 
without change over a variation of speed of between 50 and 100 words per minute. 

As already intimated, the tension of the armature-spring of the restoring- 
relay R R and the play between its contact points should be greater than that of the 
sixth-pulse or printing relay. Adjustable tension springs are used on these relays. 
When a marked variation in the speed of transmission occurs, some adjustment of 
the governing-relay is of course necessary. The lower the speed the stronger the 
pull or push of the spring should be to secure prompter action of the armature-lever, 
since otherwise the lever would perhaps be drawn to its contact point by a short 
pulsation. Contrariwise, when the speed of transmission is high the pull of the 



BUCKINGHAM PRINTER. 



436^ 



spring must be reduced in order that the armature may get forward to its contact 
point at the proper time. The selecting-rehiys each have two electromagnets, but 
have no retractile springs, as the reversed winding of their coils effects the same 
purpose, and with the advantages that the effect of the armature-springs has not to 
be overcome, and that the repelling magnetism of one of the cores assists in the 
movement of the armature-lever. It also insures that the relays will stay in a given 
position until the current that reverses the position of the armature actually passes 
through the coils. 

Type-wheel Setting Appakatus. — The manner in which the type-wheel is 
brought into any one of the 32 possible positions is perhaps the most unique of the 

FIG. 3252. 




THEORY OF TYPE-WHEEL-MOVING APPARATUS. 



numerous novel and ingenious features of the Buckingham printer. The electro- 
mechanism for this purpose is schematically outlined in Fig. 325^'. The type- 
wheel v^ is securely mounted with a dogging-cylinder v on a horizontal shaft. 
This shaft receives an endwise motion from the horizontal levers on the left, 
and a rotary motion from the horizontal levers on the right. 

Type-magnet Xo. 3, which is operated by selecting-relay Xo. 3, is shown as a h 
at the right of Fig. 325?*. The means by which its arm 3 is connected to tlie type- 
wheel levers and to the armature is clearly outlined in the figure. The other arms 
are similarly connected to their respective type-magnets, which latter are also 
operated by their respective selecting-relays (which likewise act as the type-maguet 
restoring-relays), as indicated in Fig. 325^'. 



436/ 



AMERICAN TELEGRAPHY. 



In shop phrase, these horizontal levers are termed whiffletrees. The vertical 
arms 4, 5, connected with their type-magnets 4, 5, move the horizontal levers which 
give the endwise motion to the type-wheel. The arms i, 2, 3, connected with type- 
magnets I, 2, 3, move the right-hand levers, which impart, by suitable intervening 
mechanism, rotary motion to the type-wheel. The type-wheel shaft is attached ly 
a swivel connection to the left-hand levers. This swivel is shown separately at h 
above dogging-magnet M. 

The whiffletrees are connected by suitable links and pins to their respective 
arms, and, as indicated in Fig. 325/, are so pivoted and interlinked that a movement 

of arm 5, for exam- 
FiG. 32 -y, pie, to the right will 

move the type- wheel 
a distance equal to 
the width of one of 
the type- wheel rings 
to the left. AVhen 
arm 4 only is moved 
it shoves the type- 
wheel shaft length- 
wise a distance of 2 
rings of the type- 
wheel to the right. 
When both arms are 
moved together the 
type- wheel is moved 
a distance equal to 
one ring to the right. 
,^J^ As in the normal position of the type-wheel the second ring from the 
" right is in the printing position, it is clear that either of the three other 

rings may be brought into a printing position by the single and combined effect 
of the two endwise adjusting-arms. 

The movements of the right-hand levers to the right or left impart a rotary 
motion to the type-wheel shaft by the intermediary of the spiral slot in a sleeve c 
through which a pin d' attached to a rod w projects, ^rhis rod is connected by a 
link to the right-hand whiffletrees. The type- wheel shaft enters the left end of the 
same sleeve, in which it moves freely lengthwise. The sleeve itself turns on suitably 
supported ball bearings (not shown) in the groove t. A pin d on the type- wheel 
shaft projects through a straight slot in such a manner that when the sleeve rotates 
in either direction, the pin compels the type-wheel shaft to turn with it. The 
rotating levers are so adjusted that arm i, when moved alone to the left, by its mag- 
net will turn the type-wheel, as a whole, one half of a revolution in the direction of 
the arrow^ shown at t. Arm 2, when moved alone to the right, turns the type- wheel 
two eighths of a revolution in an opposite direction. Arm 3 moved alone to the 
right turns the type-wheel one eighth of a revolution in the same direction as arm 2. 
Arms 2 and 3, acting together, turn the type-wheel three eighths of a revolution in 




TYPE-MAGNETS, 



BUCKINGHAM PRINTER. 436^ 

a direction opposite to the arrow, while arms i and 2 acting at the same time, but 
oppositely, will turn the type- wheel two eighths of a revolution in the direction of the 
arrow ; and by these means, as already intimated, any one of the characters on the 
type- wheel may be placed in the position for printing Avith a maximum of five pro- 
longed pulses, apart from the final prolonged negative pulse for printing and 
restornig the apparatus to normal after printing. 

The dogging-magnet M shown above tJie type- wheel plays an important part 
in adjusting and steadying the type-wheel for and during the process of printing. 
This it does by means of the small cylinder v on the same shaft as the type-wheel, 
ou the surface of which cylinder 32 small holes are arranged to correspond as to 
number and relative position with the characters on the type-wheel. When the 
dogging-magnet is operated, which will be after a desired letter is in the printing 
position, its armature drives a pin or dog D having a cone-shaped point into one 
of these holes, thereby adjusting and locking the type-wheel in the desired position, 
until the printing is effected, when it will be released by the opening of the circuit at 
the armature of the sixth-pulse relay. The spiral spring sliown retracts the pin 
after printing. 

It may be noted that each of these various movements of this apparatus is effected 
with a strong positive motion, the pull of the electromagnets upon their respective 
armatures being equal to several pounds. Nevei-theless, the different operations are 
carried out with almost mathematical 23recision, and any slight deviation from such 
precision is corrected by the dogging-pin d in the manner stated. 

As previously noted, the letters and other characters of most frequent occurrence 
in the English language are allotted the least number of prolonged pulsations in the 
Buckingham alphabet. It will also be observed that the arms which have to move 
their levers the greatest distance are placed the nearest to the beginning of a cycle of 
operation of the circuit-closing levers /j. Fig. 325/^, in the formation of the combi- 
nation of a letter. For example, type-magnet arm i. Fig. 325/, which is required to 
rotate the type-wheel a half of a revolution, is primarily operated by 'No. 2 circuit- 
closer, etc. Further, to insure correct action, the arm i is furnished with a retractile 
spring which accelerates its setting movement and retards its restoring movement. 
Arms 4, 5 also have springs that hasten their setting and retard their restoring 
movement. By these various devices the action of the different adjusting and rotat- 
ing arms is assured before the printing and restoring apparatus can come into play. 

The Buckingham Page Printer. — Details of this apparatus are shown in 
Figs. 32 5^' to 3250, similar parts having the same reference letters, and these figures 
may be considered together. The general appearance of this printer is outlined in 
Fig. 325^. In the page-printing telegraph system previously described, page 430, 
the paper carriage is moved back and forth in a manner practically similar to the 
ordhiary typewriter. That is, at the end of a line the carriage is six or eight inches 
away from the starting-point of a new line. To avoid the loss of time due to this 
arrangement, and to simplify the mechanism generally, the telegraph blank of the 
Buckingham printer is arranged in the form of a tube, which is placed over a fixed 
tubular support (<7, Fig. 325/j), which is firmly upheld by tlie bracket Z>. M is the 
dogging-magnet, d is its armature-lever. The press-magnet p m is placed at the 



436r 



AMERICAN TELEGRAPHY. 



right end of the supporting-tube a, as shown. Its lever is connected with the crank- 
lever of the printing-platen Avithin the tube, directly under the type-wheel, by means 
of a strip of rattan f , which substance, singularly enough, has been found the most 
suitable for this work, m is the manually operated rod referred to in connection 
with Fig. 325/^. This rod is provided with a frictional locking device at its left end 
A, which holds it in a given position, either forward or back. 

The paper tube is slid over the left end of the tube a. A row of small holes 
(A, Fig. 325??^) is perforated in advance along the margin of the paper tube, and the 

FIG. 325/^. 




BUCKINGHAM PRINTER — SIDE VIEW. 



teeth of a small star- wheel, / in other 
figures, are caused to mesh into these 
holes, j is the priuter escape-wheel 
controlled by the printer escape-mag- 
net m'. On the same shaft with j 
{see Fig. 325^) there is a spur-wheel 
i, which gears with a pinion k, the 
latter on a shaft with wheel k', which 
meshes with an annular ring /. The 
driving power of this train of gear- 
ing is furnished by an electric motor 
N that turns a vertical shafts?', which shaft by means of a bevel gear/' g tends to 
wind up a recoil-spring Ji, one end of which is attached to the shaft d, the other end 
to the shaft on which the printer escape-wheel / and spur-wheel i are mounted. 
When the spring is fully wound the motor stops, the force employed permitting this 
without injury to the mechanism. 

The star- wheel is carried on the inner side of the annular ring I, Fig. 3250. 
The clock-work gearing operated by the motor-wound spring gives the annular ring 
a tendency to rotation, which, under control of the printer escape-magnet m', becomes 
a step=by-step movement. Thus, while a message is being printed letter by letter, 
this annular ring and with it the star- wheel are moved around the supporting- tube 



BUCKINGHAM PRINTER 



436^ 



FIG. 325/. 



(the star-wheel being held in one axial position at this time b}^ the engagement of 
some of its teeth in three circumferential grooves, t^ s, r, on the supporting-tube, 
I^^i§'- 3-5'^^)^ until at the end of a revolution the star-wheel is almost at the place ot" 
beginning. Since the star-wheel teeth are, as stated, meshed with the perforations 
in the paper, the latter is also carried around the fixed support step by step, and thus, 
as printing goes on, a new surface of the paper is uniformly fed below the type-wheel. 
On the annular ring there are 74 teeth (sufficient to carry the ring once around the 
tube), whicli corresponds also with the number of letters and sj^aces on one line of a 
telegraph blank. The annular ring / is upheld by grooved roller bearings n n^ which 
run on flanges on the periphery of the ring, the teeth of the latter being placed on 
the centre of the periphery (Fig, 3250). 

It is seen that the grooves z', 5, ?', on the tube a^ turn off at an angle or incline 
V w' x', at a point. Fig. 325/, which corresponds with the end of a line on the 
paper. When the star-wheel in its course passes through 
these iuclined grooves it perforce turns on its axis, causing 
its teeth to mesh with new perforations in the paper, and 
advancing the paper tube thereby the distance of one line 
along the supporting-tube. This action is brought about 
quickly as follows: Near the zero point several teeth are 
omitted from the escape-wheel /. At the time when the 
star-wheel/ arrives at the entrance of the angular grooves, 
that portion of the wheel/ from which the teeth are 
OQiitted reaches the escapement-pawls 4 and 5 (Figs. 3250, 
325/;), whereupon that wheel and with it the annular ring 
jump a corresponding distance, with tlie result that the 
paper, as just stated, is advanced a line, with but one step 
of the escape- wheel — in other words, with but one pulse 
of current. 

In Fig. 325?^?, which is a top view, t is the paper tube, a is its tubular support. 
The perforations h in the margin of the paper tube are prepared in advance, w is 
the type-wheel, and at its left v is the dogging-cylinder. The printing-platen is 
within the tube, and in printing it strikes the paper through the aperture e in a (Fig. 
325/). Normally a slot u' is directly below the star- wheel /, so that when the at- 
tendant slips a paper tube over a, the first holes h h in the paper easily mesh with the 
teeth of the star-wheel. In order that after the star-wheel has passed the angular 
grooves v\ tv', x' (shown in previous figure) its teeth may not catch in the edges of 
the grooves at the slot 21', at the commencement of a new line, the slot is placed a 
short distance to the left of the angular grooves. There is, hoAvever, another device 
to insure that the teeth of the star-wheel / shall always be in the position to clear the 
edges of the grooves at this slot, namely, the pin 0, Figs. 325?^, etc. This pin is 
normally in such a position that just before the star- wheel enters the slot the pin enters a 
space between two teeth of the star- wheel, and puts those teeth in positive alignment 
with the grooves /, s, r. Inasmuch, however, as when thepaper tube is being placed 
in position for printing its perforations have to mesh with the star-wheel, it is evid(mt 
that the pin would be in the way of this action. Therefore at this time it is moved 




436/ 



AMERICAN TELEGRAPHY 



FIG. 32^fn. 



out of its normal position by the extension s' (carried on a slide-bar) by means of the 
small chain and pulley, d i, Fig. 325//^, and^j, Fig. 3250, which are actuated each time 

the attendant manually pulls 
out the rod m {see Figs. 325/^, 
325^). When this rod is 
pushed in by the attendant 
the pin is returned to its 
normal position, j)lacing the 
teeth of the star-wheel into 
alignment with the said 
grooves, assuming that the 
act of inserting the paper 
tube might have placed the 
teeth out of alignment. 

A section of the paper 
tube with the holes It Ji, and 
the manner in which the 
star-wheel /meshes into these 
holes and with the grooves 
t, s, r, are also indicated in 
Fig. 325 ?i ; also the middle 
section x of the tubular sup- 
port. The tubular support 
a is divided into three sec- 
tions, w, X, y, Fig. 325^. 
The left - end section is of 
slightly less diameter than the 
right end, to facilitate passing 
the paper tube over it. The 
end sections lu and y are of 

brass tubing; the middle section x is of iron, and is of sufficient thickness for the 

circumferential and angular grooves cut in it, as indicated in Fig. 325 ;i. 
Fig. 3250 is an end view of the tube a, 

printing-platen p, the star-wheel adjusting-pin 

0, and the pulleys and chain which operate it 

by the manually operated rod m, etc.. When 

this rod m (shown in end view in this figure) 

is pushed in, that is, to the right, it engages 

with a stop p on pulley p\ which causes the 

chain to move the pin out of the path of the 

star-wheel. When the rod is withdrawn the 

bent spring li restores the pin to its normal 

position for the purposes just noted. 7i n are , . , a 

the roller bearings on which the annular ring turns; b' is the bracket by which tho 

star- wheel / is attached to the annular ring. A device which is employed to cushion 




FIG. 325^. 




BUCKINGHAM PRINTER. 



436?/ 



FICx. 325^7. 



the blow of the printing-platen on the type- wheel is also shown in this figure. It con- 
sists of an endless rubber band h, which runs over two small wheels at the top and a 
pulley c at tbe bottom of the tube. A ratchet-wheel is mounted on the pulley shaft; 
d' is its pawl. An arm a' extends from the printing-lever p, as shown, and at every 
downward movement of the lever this arm engages witli a tooth of the ratchet-wheel, 
thus turning the rubber band to present new surfaces to the platen, thereby jDrevent- 
ing undue wearing of the rubber at any one point. The wearing process is, however, 

very slow, and the 
pawl and ratchet can 
be detached if desired. 
A side, end, and 
sectional view of the 
step-by-step and the 
printing and related 
apparatus are given 
in Fig. 2>-SP- ^1^ this 
p is a side view of the 
printing crank-lever. 
Instead of tlie conven- 
tional curved escape 
device shown at j. 
Fig. 325 A, the escape- 
wheel j in practice is 
provided with two 
pawls, 4, 5. These 
pawls are supported 
by a vertical arm e' 
from armature R of 
printer escape-magnet 
m', and are shown just 
below j. Pawl 5 is 
fixed on e'; pawl 4 is 
movable on an axis 
h'. It will be seen 
that when armature E 
is attracted pawl 4 is disengaged from a tooth of the escape- wheel /, and that at the 
same time pawl 5 moves to the right in the path of a tooth. Tliisonly permits a very 
slight movement of the escape-wheel. When, however, pawl 4 is disengaged it is 
turned on its axis by the spring q^ a short distance in a direction opposite to that in 
which the escape- wheel / rotates, so tliat it comes into line witli the space between 
tlie teeth next back of that in which pawl 5 now rests. Hence, when the armature 
R is retracted and pawl 4 disengages from the wheel /, the wheel will advance one 
step before it is held by pawl 4. This peculiar movement insures that the paper tube 
will not be fed until after the letter is printed; that is to say, when the armature of 
escape-magnet m' is attracted by the closing of the sixtli-pulse relay of the system 




436z; 



AMERICAN TELEGRAPHY. 



(at which time the printing is effected), the escape-wheel does not make a full move- 
ment, and consequently the paper tube is not advanced, but when the letter is printed 
and the armature R of m' is retracted, the paper is then fed. 

In the operation of receiving messages by this system, the attendant places the 
telegraph blank in its tubular form over its support « until it meshes with the star- 
wheel as stated. The reception of a message then proceeds. At the end of the first 
line, which contams the number, origiuatiug station, and date of the message, also at 

FIG. 325/. 




the end of the address, and at the end of the message, a double or line space is pro- 
vided in the perforated strip at the transmitting end. At these intervals the atten- 
dant operates the manual device m by the knob a, and advances the paper tube one 
line. 

It is essential at such times that means be provided whereby the pawls 4, 5 may 
be readily discoimected from their escape-wheel j, so that it, as well as the annular 
ring /, and with it the star-wheel / and the paper tube, may be quickly brought to the 
zero or unison position. The apparatus for this purpose is shown in Figs. 32 5 A,-, 325^^^. 



BUCKINGHAM PRINTER. 4.T,6w 

It consists of an arm u attached to the right end of the manually operated rod m, 
which engages with a groove d cut in the hub of the escape-wheel _/. On the right 
end V of this hub is cut a slot, through which a pin ?/ projects. This permits the 
escape-wheel to be moved a certain distance endwise on its shaft. Upon an auxiliary 
disc attached to j there is a flat tooth e', whose end normally clears a fixed stop e. 
When, however, the rod 7)i is pulled to the left, thereby drawing with it the escape- 
wheel j, and freeing the latter from its pawls, the stop e is in the path of tooth e' 
and holds the wheel j at a point which corresponds to tlie unison point, namely, 
the point at which star-wheel / will be in line with the slot u', Fig. 325/. In order 
to avoid the shock which would ensue to the apparatus if the gearing were allowed 
to run without check of any kind, when the escape-wheel is thus released from its 
pawls, a fly F is caused to make a clutch connection at r r with the shaft of j at the 
instant of said disconnection, which effects the desired result. It is also essential 
for the proper working of this paper feed apparatus that when it is thus allowed to 
run to zero or unison position, the fixed pawl 5, and not the movable j)awl 4, shall 
be in the path of a tooth of ;. Hence, when disengagement of the escape-wheel j 
with its pawls is made, armature K is assumed to be attracted, which will bring 
pawl 5 in the path of a tooth. 

An expert attendant quickly detects any imperfect signals, such as might be 
caused by wire trouble of any kind, by a break in the rhythm of the working of 
the receiving-apparatus of this system, and in the event of any appearance of error 
he signals to the transmitting operator accordingly. In this way incipient errors 
due. to line and instrument troubles are detected with practice^ lly the same facility 
as is the case on the regular Morse circuits. 

The rate at which messages are regularly transmitted between New York and 
Chicago, a distance of 974 miles, by the Buckingham printing telegraph on a duplex 
circuit, averages over 80 words per minute in each direction. This is equal to 200 
messages of the average length per hour on one wire. The ordinary Wheatstone 
repeaters are inserted at Bufi'alo, Avhich is 444 miles from New York and 532 miles 
from Chicago. The wires used are the ordinary overhead copper wires of the com- 
pany, measuring about 5 ohms per mile, and the system is of course operated under 
all the prevailing conditions of capacity, self-inductance, and induction effects 
from other lines to which the contiguous circuits may be subjected. On several 
occasions the system has been worked at full capacity, to test its accuracy of trans- 
mission and reception. The niatler transmitted on these occasions consisted of 
ordinary newspaper press re[)orts, and were received on sheets of foolscap. On the 
first test, from Chicago to New York, 2429 words were transmitted in 23 minutes 
54 seconds; on the second test, 6073 words were sent and received in 60 minutes 
13 seconds; on still another occasion 9126 words were sent in 91 minutes 18 seconds, 
without error in the printed copy. This is at an average I'ate of 100 words per min- 
ute. These figures include time lost in changing the sheets, which required six sec- 
onds for each change. By improvements in the apparatus this time has been re- 
duced to one second. 

The ^vriter desires to express his obligations to Mr. Buckinglunn for facilities afforded 
him in gathering the foregoing data concerning this interesting and ingenious system. 



43^x 



AMERICAN TELEGRAPHY. 



The Baudot Multiplex Prixter. — This system is employed by the Freiicli 
Government on all of its most important lines. For its mnltiplex feature it employs 
synchronism and a trailer and segmental wheels or discs, practically similar to that 
shown in Fig. 256, certain segments being set apart, in series of 5, at intervals 
around the wheel, for each transmitting and receiving instrument, of which there 
are usually 4 to each circuit. On short circuits 6 sets of apparatus may be thus 
operated. Hence 4 or 6 messages may be sent practically simultaneously by this 
system. For each letter transmitted a combination of 5 positive or negative pulsa- 
tions of equal duration is employed. A letter is transmitted by depressing a cer- 
tain key or keys of a key-board, which thus sends out the desired combination of 
pulsations for a given letter. At the receiving station these pulsations operate one 
or more of five polarized relays corresponding to the keys depressed, and these relays 
in turn, by their armature-levers, close certain local circuits which control mechan- 
ism whereby the given letter is selected and printed on a paper tape. While this 
given letter is being printed on one receiving instrument the line is being utilized 
for the transmission of another letter on another instrument. S3mchronism is main- 
tained by suitable correcting devices. The rate of signaling by this system is about 
30 words per minute on each set of instruments, or, for a circuit, 120 words or 180 
words per minute, depending on whether it is arranged for quadruplex or sextuplex 
transmission. (Described at length in Thomas's Traite de Telegraphique Electrique.) 

The Rowland Multiplex Page Prijs'ter. — This printer in its latest form 
is arranged to transmit 8 messages at once, 4 in each direction, the circuit being 
worked duplex. For the multiplex transmission a segmental wheel or cylinder 
and trailer are used, certain segments being disposed in series of 11 around the cylin- 
der for the respective transmitting and receiving instruments. In this system 11 
pulsations of alternating polarity are utilized for the transmission of a letter, two given 
pulsations out of the cycle of 11 being omitted for a given letter. Selecting-magnets 
in a local circtiit operated by a main-line relay select the letters transmitted, the 
message being printed in page form. A manually operated key-board transmitter is 
employed for each set of instruments, the depression of one key setting up the 
necessary combination of omitted pulsations for a given letter. The alternating 
currents for the operation of this system are set up by a dynamo machine. A 
motor at each end of the circuit is employed to drive the trailer, and these motors 
are governed by the pulsations from the dynamo machine, by which means synchro- 
nism between the sending and receiving apparatus is secured. The rate of signaling 
by this system is given as 30 words per minute on each printer, or a total of 240 
words per minute. This printer is in successful operation (1908) in Germany and 
Italy as an octoplex, and on several circuits of the Postal Telegraph Cable Company 
in this country. For instance, as an octoplex between Kew York and Boston, New 
York and Philadelphia, Chicago and St. Louis, and as a quadruplex between Xew 
York and Chicago, with repeaters at Meadville, Pa. Details of this printer will 
be found in a paper by Mr. Louis M. Potts (Trans. Am, Inst EL Engineers, April, 
1907). 



THE BARCLAY LONG-DISTANCE PAGE PRINTER. 437 

The Barclay Long-Distance Page Printer, 

This printer, due to Mr. J. C. Barclay, is now employed extensively on the 
lines of the Western UnxOn Telegraph (Company and has been adopted by that com- 
pany. The messages are received on a telegraph blank by an ordinary typewriter. 
Fig. 325^ is a theoretical diagram of the system. Up to a certain point this prin- 
ter corresponds to the Buckingham printer, already fully described in the imme- 
diately preceding pages. Thus it employs a perforated tape (perforated by a key- 
board perforator) by means of which the elements of a letter are transmitted and 
the selection and printing of the characters are effected by a cycle of six pulses of 
varying lengths, the Buckingham alphabet beijig used. The transmission of these 
pulses results in the operation of a polarized relay E, Fig. 3255', in the main line. 
This relay by its armature controls local circuits in Avhich are a governing or sepa- 
rator relay ge, a nnison or synchronizer magnet UM, and an escapement magnet 
EM, which latter magnet imparts the step-by-step motion to the sunflower or dis- 
tributor D on shaft s, thereby actuating the circuit closers i, 2, 3, 4, 5, 6, with the 
result that, as stated on page 436c, one or more selecting, or distributing relays, 
de', de% de^, de\ de', are operated. It is at this point the Barclay printer deviates 
from the Buckingham. In the case of the last named printer the selecting relays, 
by energizing certain type-magnets, cause the operation of certain levers that in turn 
bring a desired letter on the type-wheel to the printing position. 

In the. Barclay printer it will be seen by reference to Fig. 32 ^q that the arma- 
ture levers of the selecting relays control the operation of a series of contact switches 
cs^, cs^ etc., which switches, depending npon their respective positions, close a given 
circuit to one of the printing magnets pm. Each of these printing magnets is, by 
means of its armature lever, not shown in the figure, in mechanical connection with 
the type- wheel of a Blickensderfer or other suitable typewriter, and when the cir- 
cuit of a given printing magnet is completed by the closing of the sixth circuit clos- 
ing lever 6 on the sunflower, or distributor D, that printing magnet is operated and 
a given letter is printed exactly as if the key of the typewriter had been depressed 
manually. A given letter or other signal is selected for printing by the routine 
in which the long and short impulses of a given series of six pulses arrive 
(see pages 436^*, 436^^). When none of the pulses of a series is prolonged 
none of the distributing relays is affected, and the position of the switches 
cs', etc., controlled by those relays is as shown in the figure, in which case 
only the sixth pulse relay sp, the type release magnet te, and the spacing 
magnet SM are energized, as may be seen by tracing the circuit from the battery 
b' through lever 6 of the sunflower D, to wire w, to the armature lever of the sixth 
pulse, or restoring relay sp, to and through the armature levers of the distributing, or 
selecting relays, thence to the type release magnet te, to and through the spacing 
magnet sm to earth. The sixth pulse, or restoring relay sp, controls the restoring 
circuit of the selecting, or distributing relays, dr', etc. Eelay sr, it will be seen, is 
in a multiple circuit with a printing magnet when any one of them is selected, but 



437^ 



AMERICAN TELEGRAPHY. 



by a suitable adjustment of the spring of the armature-lever of relay sp and the dis- 
tance through which the lever travels, the selection and printing of a given letter 
are assured before the armature levers of the distributing relays are restored to nor- 
mal position by the closing of the contact c of relay sp. (See reference to govern- 
ing relay, page 436m, as to adjustment of spring for a somewhat similar purpose.) 

FIG. 325^. 




BARCLAY PRINTER, THEORY. 

The spacing between the printed letters on the typewriter is done automatic- 
ally, and practically concurrently with the printing of the letters, by the operation of 
the spacing magnet sm, which it may be seen is normally in the common return circuit 
of the printing magnets and consequently is operated each time a printing magnet is 
energized. The spacing between words is effected also by the spacing magnet s:m, 
which is then operated by a " spacing^' signal consisting of six short pulses. As 
stated, these short j^ulses will not operate any of the selecting relays DR. Hence 
the position of their armature levers will be as in the figure, at which time the cir- 
cuit, as joreviously noted, is completed from battery b' by way of circuit closer 6, to 
and through contact switches cs, to and through type release magnet tr, to spacing 
magnet sm which operates the spacing mechanism of the typewriter. 



THE BARCLAY PRINTER. 437^ 

• 

In tlie Blickensderfer typewriter employed for printing in the Barclay system, 
the type-wheel xw is somewhat like the type-wheel of the Buckingham printer. It 
has two parallel rows of type on the surface of a small cylinder. One of these rows 
consists of letters, the other of figures and punctuation marks. Normally the type- 
wheel of the Barclay printer is set for letter printing. When figures and certain 
punctuation marks are to be printed the position of the type-wheel is shifted by 
moving a shaft T on which it is fixedly mounted. This shaft is moved the desired 
distance for printing figures by means of a system of levers actuated by the armature 
of the shift-magnet xs as outlined in the figure. To select and operate the shift- 
magnet a shift-signal consisting of two long impulses of current followed by ono 
short and three long impulses is transmitted and consequently certain armature 
levers of distributing relays dr', etc., are moved to the left, thereby completing a cir- 
cuit from the sixth pulse circuit closer 6 to the shift relay TS. To insure that the 
armature lever of the shift-magnet xs shall remain shifted until properly released, 
its armature lever is held down by a detent lever dl, actuated by the type release 
magnet TR. This continues until a spacing signal is sent, whereupon the type re- 
lease magnet, which is in series with the spacing magnet sm, withdraws the detent 
from the armature lever of shift relay xs. When the shift-magnet has been oper- 
ated any desired figure or punctuation mark may then be selected and printed by the 

v; 

— w* 

— x/ 

Y* 

— Z" 

• — - 

B\perFeed — — — 
Carriage Return - — — 

BARCLAY COMBINED LETTER AND FIGURE ALPHABET. 

transmission of the proper signals, which, it will be seen by the accompanying alpha- 
bet of the combined letter and figure code, correspond to the letter code. For in- 
stance, when the shift-magnet is set for figures the transmission of the code signal 
for the letter T will print the figure 5, etc. 

As the typev/riter used in this system, is an ordinary page printer it is necessary 
to employ magnets to operate the carriage return, the line spacing, and paper-feed 
apparatus. When the proper signal is transmitted, at the end of a line, for instance, 
magnet CR operates the carriage return apparatus. In order that magnet en may 
not be de-energized during the return of the carriage by the action of the restoring 
relay circuit upon the distributing relays, the restoring circuit of those relays is 
opened at this time at the armature contact c' of magnet or and continues o^ten at 



A-_- 


Hi 


09 


B® - - - 


I 8.._ 


po 


c •• 


J ' 


Q' 


D« 


KC 


R* 


E3 — 


L> 


S* 


F% -. . 


M? 


T5 


G' 


N* 


U' 


Space — 




B\PEF 


Type Shift — 


• 


Carr 



437^ AMERICAN TELEGRAPHY. 

that point until the carriage, indicated by g, reaches its starting-point, where a lever 
GL engages with a lever I aud thus mechanically opens the circuit of magnet ck. 
This allows its armature to fall back and close the restoring circuit at point c\ As 
soon as the carriage begins its movement to the left the contact at point I 
closes automatically. The paper line feed mechanism, which may consist of a va- 
riety of devices, is operated by the magnet pf, which is selected for operation by a 
prearranged signal. The mechanical operations, such as the carriage return of the 
typewriter, are facilitated by electric motors practically as used in the Blickensder- 
fer electrically operated typewriter. 

The local batteries used are indicated in Fig. 325^ by the conventional symbols, 
but in practice the source of e.m.f. is a dynamo machine or storage battery. In 
practice also certain auxiliary apparatus, for example a paper- feed assist magnet and 
a shift assist magnet, are employed, but for clearness are not shown in the figure. 
Condensers around contact points and resistances and fuses are also employed prac- 
tically as shown in Fig. 3257^. The time taken in changing the message blanks on the 
typewriter is from one to two seconds. According to Mr. Barclay the rate of trans- 
mission by this printer is approximately 100 words per minute in eacli direction, the 
system being usually operated as a duplex. On long circuits Wheatstone repeating 
relays are employed at the repeating stations (see Fig. 232). 

This system has been operated experimentally through seven duplex automatic 
repeaters between New York and San Francisco. It is now in regular successful 
operation between New York and Chicago, New York and Boston, New York and 
Atlanta, Chicago and St. Louis, and numerous other points on the lines of the West- 
ern Union Telegraph Company, and its use is being rapidly extended upon those 
lines. 



the murray printing telegraph. 43 7<^^ 

The Murray Rrinting Telegraph. 

Tliis system 's clue to Mr. Donald Murray. It was for some time in experi- 
mental operation on the lines of the Postal Telegraph-Cable Company of this country, 
and is now in practical operation in the British Post Office telegraph service and else- 
where. 

The characters representing messages to be transmitted by this system are perfora- 
ted on a paper strip by a keyboard perforating-machine. This prepared strip is caused 
to send given combinations of electrical pulsations for each letter over a main line, 
which pulsations, or the omission of pulsations, operate or control receiving apparatus 
at the receiving station. This apparatus in turn is caused to perforate another strip of 
paper, which paper is then passed before a set of metal strips that in their operation, 
and depending upon the position of the perforations on the paper, select a certain letter 
of a typewriter; the message being thereby printed in page form. Fig. 325/* is a 
theoretical diagram of the apparatus and circuits at the transmitting and receiving sta- 
tions of this printer. The Murray transmitter somewhat resembles the Wheatstone 
transmitter, but employs only one vertical rod, i. This rod is carried by a thrust 
lever 9 on lever 3 and finally receives its vertical movements from the lever 3, pivoted 
at 4. Lever 3 is caused to oscillate by the lever 6, attached to the cam 21, which 
cam, Avith star- wheel 15, receives motion from a phonic wheel 26 (see Fig. 255, 
page 337)- Lever 2 carries a tooth 7 that rests against the pin 8 on lever 3. When 
the transmitter is in operation the rod i makes a complete or partial upward stroke, 
depending on the presence or absence of holes in the paper strip 20. When the paper 
strip does not limit the upward movement of rod i, the end 9 of lever 2 impinges on 
lever 11, pushing lever 13 against contact point 18. When the rod i is restrained 
from making a complete stroke by the uncut paper strip, the end 9 of lever 2 is 
forced upward against lever 10, pushing lever 13-jigainst contact 19; thereby either 
reversing the battery or putting the line to ground, as may be prearranged. A suc- 
cession of holes in the paper merely results in holding lever 13 against contact 18; 
whereas the eifect of a succession of unperforated parts of the paper is to hold that 
lever against contact 19. The jockey rider 17 holds lever 13 firmly in either posi- 
tion. The paper strip is moved forward by the star-wheel 15 by means of the small 
central row of holes in the paper, which are punched in advance of and separately 
from the regular message perforations (see, for instance,- Fig. 325^?). 

Unlike the characters of the Morse alphabet or of the Buckingham code, the 
elements forming the letters, figures, and other signals of the Murray alphabet are of 
equal length ; there being five units for each letter, or other characters of that al- 
phabet. This fact admits of the use of a perforator that does not require a variable 
feed device, in which respect it differs from certain other keyboard perforators 
(see page 436O. These five units occupy half an inch lengthwise of the paper 
strip, as indicated by the transverse lines shown in the figure. The location and 
number of the perforations within this space vary with each letter, and upon the 
position and number of these perforations depend the length of and routine in which 
pulsations of current shall pass over the line, which pulsations in turn determine or 
select the letter or other signal to be printed. Thus in the figure the last five com- 



437- 



AMERICAN TELEGRAPHY. 



binations of holes in the paper strip at the collector represent the letters forming the 
word Paris. To indicate the quality of the positive and negative pulsations pass- 
ing to line the following device is provided. An eccentric wlieel 5 makes one revo- 
lution for each positive and negative pulsation. If the index carried by wheel 5 
points to a given division on the scale 22 when the negative or the positive contact 
is broken, equal currents are goiug out to line. If not, the contacts are adjusted 
accordiugly, practically as in the \Yheatstone automatic system to correct a bias 
(see page 319). 

In the Murray printer there is no space between letters, hence the signals run 
into one another at times; but as the operation of the receiving part of the system de- 
pends on the time of arrival of letter and other signals, this, as we shall see, does not 
affect the proper selection and printing of such letters, etc. This printer does not 
require synchronous movement of parts at the transmitting and receiving stations, 
but it does require isochronism, or identity of speed of operation between the transmit- 
ting and receiving apparatus, which isochronism is maintained by the action of ar- 
riving signals upon certain apparatus in a local circuit at the receiving station, in a 
way to be described subsequently. 

The perforated stri^) at the transmitting station and the transmitter are termed 
tlie Collector. The apparatus which effects the maintenance of isochronism and 
the punching of the paper strip at the receiving station is termed the Distributor. 
The mechanism which selects and prints the letters and figures is termed the Trans- 
lator, all as in Fig. 325?% 

In actual practice the transmitter is caused to send out positive and negative 
pulsations of current. These pulsations operate a polarized relay at the receiving 
station, and this relay actuates a "punching" relay and a "governing" relay in a 
local circuit. To simplify the description the polarized relay is omitted in Fig. 32 5?-, 
and the punching relay and governing relay are shown as operated directly by 
makes and breaks of the main line circuit at the transmitter; the positive pole being 
placed to line at contact 18 and the earth to line at contact 19, according to the posi- 
tion of lever 13. The punching relay and governing relay are identical in con- 
struction, and consequently their armature levers move synchronously in response to 
arriving currents. The punching relay controls the operation of a puncliing mag- 
net, which by means of armature lever 29 and j)unch 30 perforates the " recorder" 
paper. The governing relay 28 controls the rate of vibrations of the vibrator 35. 
This vibrator performs two functions: it operates a spacing magnet by means of 
contact 32, and the punching magnet by means of contact 33. 

The rate of vibration of the reeds of the respective vibrators at the transmitting 
and receiving station may be varied by moving the small weights wtv, in the well- 
known way. These vibrators are operated on the well-known "buzzer " principle (see 
page 256). « In practice the reed 34 at the receiving station is given a tendency to 
vibrate at a rate 2 or 3 per cent, higher than the transmitting vibrator, but the re- 
spective vibrators are maintained at a practically equal rate of vibration, by an in- 
genious retarding device applied to vibrator 35, as follows. The reed 23 of the trans- 
mitting vibrator has an unretarded phase of vibration. Hence any change in the 
strength of current merely increases the amplitude of vibration, the rate of vibration 



THE MURRAY PRINTING TELEGRAPH. 



437/ 



remaining practioally uniform. The reed 34 of vibrator 35, however, is provided with 
buffers, ^6, 37, against which it impinges at each oscillation. These buffers limit the 
amplitude of vibration of the reed, and (as Mr. Murray has pointed out) as the energy 
imparted to the reed must find some outlet, it becomes very susceptible to variations 
in current strength through its coils. Normally, when makes and breaks of the 



FIG. 325^. 



j TRANSMITTING STATION 

MOTOR- (PHONIC-WHEEL i VIRRATOR) 




-COLLECTOR 



SPACE-SIGNAL* 




RECEIVING STATION 



^_ 58 FIGURE-SHIFT 57 

[TRANSLATOR ^ p\jumjwu~ij " pai^^tj-v] ^ 



PRINTER 



GOVERNING 



' ^ p^ v^ a 




DISTRIBUTOR 



MURRAY PRINTER, THEORY 

circuit or alternations of current are being transmitted, the armature levers 41, 39, 
and the reed 34 would oscillate synchronously, but for the slight tendency of the 
reed to outspeed the levers. When synchronism exists lever 41 will be on contact 
44, lever 39 will be on contact 42, and reed 34 will be on contact S3, at the one time. 
If, however, reed 34 tends to exceed the said normal oscillation of lever 39, there will 
be times when the lever 39 will be between its contacts 42, 43 ; consequently a decrease 
of current strength through magnet 35 ensues, and the rate of vibration of the reed is 
thereby retarded sufficiently to keep it in step with the relays. Further, as long as 
signals continue to arrive over the line more or less uniformly, the reed 34 effects a 
regular succession of breaks of the spacing magnet circuit at contact 32, with the 
result that the recorder paper strip is drawn along at a uniform rate by tlie star- 
wheel on shaft 31. The perforations made in the recorder paper strip are identical 
with those of the perforated paper at the transmitting station. The punch 29 



\^lg 



AMERICAN TELEGRAPHY. 



therefore must only be actuated when the rod i at the collector passes through a hole 
in the tape; and when the rod i meets a section of uncut paper, the punch 29 must 
be quiescent. These requirements are met in the followiug manner. When the 
rod I passes through, say, 3 holes in the paper in succession, a continuous current 
passes to the line during that time. Hence, during the same time, the lever 41 of 
the punching relay is attracted to its contact 44, but during this time also the reed 
34 of the vibrator has thrice opened and closed the punching magnet circuit at con- 
tact TyTy^ which punches three holes in the recorder paper corresponding to those in 
the collector paper. Obviously, if a section of uncut paper equal to, say, 3 units 
passes before rod i, no current will pass over the main line during that time. 
Consequently the lever 41 will be on its back stop during that interval, thereby 
opening the punching magnet circuit at contact 44. Therefore punch 30 is at rest 
during this time, notwithstanding that reed 34 continues to open and close its con- 
tact zi- Clearly, when lever 41 of the punching relay is on its front or back stop, 
the lever of the governing relay will at the same time be on its front or back stop, 
and for equal intervals. As already noted, however, the armature lever 39 of relay 
28 has a contact on its front and back stop. Hence whether lever 39 is on contact 
42 or 43, the circuit of vibrator 35 is closed at either j)oint. Thus the reed 34 will 
continue to open and close that circuit at contact 32 at regular intervals, thereby 
operating the armature lever n of the spacing magnet, which by actuating the star- 
wheel 31 effects a regular step-by-step movement of the recorder paj^er. By these 
means an exact reproduction of the original perforated paper is obtained at the re- 
ceiving station. When signals cease to arrive over the main line a device not shown 
in the figure automatically opens the spacing magnet at the switch 60 to prevent un- 
necessary running out of the paper. 

The manner of translating the perforations in the recorder paper into printed, 
characters will now be described. It may simplify the explanation if it be noted 
that in the operation of the various parts of the translator (Fig. 325;-) the process of 
the perforating machine at the transmitting station is here virtually reversed. In 
the operation of the perforating machine the depression of a letter key i^rojects for- 
ward a certain group of punches that perforate holes in the paper stri}") corresponding 
to the key depressed. In the selector the action of the mechanism presses backward by 
means of the uncut paper a certain group of rods, which act effects the depression of a 
key of a typewriter, and the printing of a desired letter. The selector includes a star- 
wheel 46, carried on a shuttle 47, which oscillates in the directions indicated by the 
double arrow a — b. The shuttle also carries a curved die plate which is coincident with 
the surface of star- wheel 46. The die plate has holes punched in its surface corre- 
sponding with five consecutive units or holes of the perforated paper. At each recipro- 
cation of the shuttle the star-wheel 46 is rotated a distance CD, corresponding to five 
units of the paper strip,and as the star- wheel is thus rotated the paper strip is advanced 
a distance equal to one letter. The right ends of the five rods 48 are suitably held in 
proximity to the die plate. These rods are attached to combs 49 having teeth 61. 
As the shuttle moves toward A the die plate is pushed toward the rods 48, and de- 
pending on the location and number of perforations in the paper strip a certain num- 
ber of the rods will enter the holes in the die plate and the combs attached to such 



THE MURRAY PRINTING TELEGRAPH. 43 7>^ 

rods will not be affected. But the rods wliich come against the uncut parts of the 
paper are pushed back a distance of about one-sixteenth of an inch. This moves 
corresponding combs a similar distance, thereby bringing a certain group of teeth 
or slots into alignment with a vertical bar or latch, for instance, 50 in 
the figure. There are in all 56 of these latches; one for each of the letters, 
figures, etc., of the typewriter or printer. These latches are held in front 
of, but just removed from, the teeth, or slots, by a universal bar 51, which, 
however, at a given instant is moved back in the direction r — E, allowing that 
latch, and no other, which is opposite the slots that have been brought into align- 
ment as stated, in this case latch 50, to move into the space thus provided; being 
draAvn thereinto by its spring 52. This latch i)ushes the hook 53, which is attached 
to a given type key, under a bar 55 that is oscillating rapidly in the directions in- 
dicated by double arrow h — G, with the result that the key s (in this instance) is 
sharply depressed, printing the _ corresponding letter. Similarly any other letter 
thus selected will be printed. The moment the hook 53 engages with the bar 55 the 
universal bar 51 on its excursion e — F restores the latches to their normal position, 
and the shuttle on its return by means of the plate 56, which engages with projec- 
tions from the combs, restores the rods 48 to zero position. All of these actions are 
effected at the proper instants by a battery of cams operated by suitable machinery, 
not shown in the figure. As one letter of a word is being printed while the next 
letter is being selected for printing, no actual time is lost in the printing. 

As the combinations of the five units of the Murray aphabet give only ^;^ permu- 
tatious, a " shift" signal is provided by which a shifting device is operated on the 
typewriter, whereby figures or punctuation marks in place of letters are |)rinted, or 
vice versa. The figure shift is operated by means of a sixth comb 61, not attached 
to any of the rods 48. This device is shown separately at A, Fig. 325?-. When 
the figure shift signal is transmitted the latch 58 is selected and is drawn into the 
slot, its wedge-shaped edge engaging with a sloping tooth of the figure comb and 
moving it to the left one-sixteenth of an inch, whereby the figure locks are opened 
and the letter locks are closed. Eeversely, a letter shift-signal selects the latch 57, 
thereby opening the letter locks and closing the figure locks. The letter shift-sig- 
nal consists of five holes in the paper strip. Obvigusly this permits the rods 48 to 
enter holes in the die plate. Hence no letter is selected and the printer remains 
idle. Advantage is taken of this arrangement to correct errors in the perforated 
strip at the perforating machine. Thus when the operator finds that he has perfo- 
rated a wrong letter or figure, he punches the letter shift- signal over the erroneous 
characters, which constitutes a "rub-out," and then repeats the desired letter. A 
rub-out of five letters is indicated at 59 on the recorder strip. 

The letter feed of the Murray printer or typewriter is accomplished automat- 
ically as each letter is printed. The line feed is accomplished by a " line " signal, 
which is made by the depression of a line signal key on the perforator by the oper- 
ator at the end of every seventieth letter, the occurrence of which is indicated to 
him by a letter-counting device at the perforator. This line signal operates a special 
latch at the typewriter which releases mechanism that automatically moves the ptiper 
the distance of a line. At the end of a message the operator perforates a "stop'' 



437^ AMERICAN TELEGRAPHY. 

signal. This signal runs the printer carriage back to the starting position and stops 
the printer. The attendant thereupon tears off the message and presses a button 
which starts the printing of another message. If it should be desired to repeat 
the messages thus recorded on the perforated paper to a distant station, the strip is 
passed tlirough a transmitter precisely as if it had been punched by the original per- 
forating machine. 

It is essential that the recorder paper should always present the space on the 
paper representing a given five-unit signal before the five holes of the die plate. To 
insure this result, which is termed maintaining unison, the punching operator makes 
several space signals before starting a batch of messages. The space signal, as al- 
ready intimated, is represented by a middle or third hole in the five-unit space, as 
shown at the collector and as indicated by ss at the selector. Every fifth tooth of 
the star-wheel 46 is omitted. The attendant can thus see at a glance if the space 
signal coincides with the missing tooth. If not, he retards the paper by the rota- 
tion of a unison arm, not shown, which speedily brings it into unison. The mech- 
anism of the printer is driven by a small electric motor which consumes about 40 
watts for a speed of 140 Avords per minute. 

According to Mr. Murray the maximum capacity of this printer is about 150 words 
per minute, but for various reasons the speed in practice is maintained at about 
100 words per minute. For additional details of this printer the reader is referred 
to a paper by Mr. William B. Van Syze on " A New Page Printing Telegraph" 
(Transactions American Institute of Electrical Engineers, Vol. 18), and to a 
later jjaper by Mr. Murray descriptive of his printer (Journal British Institute of 
Electrical Engineers, Vol. 34), from which paper the accompanying diagram is with 
some minor alterations reproduced. 



CHAPTER XXVI 1 1. 
FIRE ALARM TELEGRAPHY. 

aAMEWELL,GATNOK,SPElCHEU SVSTEMS.-AUXILIARY ANP AUTOMATIC EIRE ALARM TEI. 

EGRAPHY, ETC. 

The importance of electricity as a time saw iu a.moun.ing the existence of a 
dre can scally be over-estimated, since it is self-evident tl«.t the -^ P/^f^ ^ 
fire can be attacked by the firemen the more easily it can be subdued and that with 

the minimum of loss. , . 

There are but few cities of any importance in tills country to-day that aie not 
equipped with a fire-alarm telegraph system. The days of the fire observation tower, 
with a watchman patrolling its topmost platform on the lookout for signs o ncip^ 
ient conflagrations, have, it may be said, passed, although in several '^"'f «',« ^IJ 
towers still remain, and in some instances are utilized as a support tor a fire bell, 
which now is rung, either to announce, by the number of its strokes, the location of 
an alarm box, or to "strike" certain hours of the day and night; the strokes of the 
hammer being caused by impulses of electricity in a manner to be described sub- 

''"^Trespecial advantage of a fire alarm telegraph system is that it not only gives 
the alarm of fire with the minimum loss of time but also indicates to the firemen the 
location of the fire within a very short distance. . 

A simple fire alarm telegraph system consists of a central oflice, or station, in 
which alarm apparatus and battery are located, and of signal boxes in the street and 
elsewhere, by which to transmit alarms to the central office, and a wii-e connecting the 
central station with the various signal boxes in the streets, in fire-engine stations, 

and elsewhere. ,, 

Such a " svstem" is outlined iu Fig. 326, in which R is a relay and G a bell, con- 
trolled by B, in the central office. ,.b is the main battery for the circuit, sb are street 
sio-nal boxes. Normallv, the fire .alarm circuit is closed. 

- ° L, each street box "is placed a " make and break " wheel resembling that used m 
■ the call boxes of the district messenger service already described. Li fact, the ordi- 
nary fire alarm telegraph systems and the district messenger systems^ .are practically 
similar in principle; the main difference between them being th.at, in the fire alarm 
telegraph service, owing to the exposed positions of the street boxes and the gTeater 
importance of the service as a whole, more substantial bo.xes and additional testing 
apparatus, etc., are employed tlian is necessary iu the district service. ^ 

The mechanism of the tire alarm signal boxes is set in motion in various ways. In 
some boxes a lever or crank is used, which, on being " pulled ," winds up a weight, 
or a sprino. within the box, the unwinding or falling of which spring, or weight 



43:1 



438 



AMERICAN TELEGRAPHY. 



causes the break-wheel to open and close the entire circuit a pre-determined number 
of times, depending upon the construction of tlie break-wheeh These makes and 
breaks of the circuit open and close the alarm apparatus in the central office and, as 
will be described, in bell towers and elsewhere, and the bells and gongs are struck a 
number of times, corresponding to the breaks in the wheel of the signal box. As in 
the case of district call boxes, each fire alarm box is assigned a designating number. 
One form of a street fire alarm box with doors open is shown in Fig. 327. 

In general these signal boxes are now supplied with an outer and inner door, as 
•indicated in that figure, to protect the electrical apparatus from the elements. 

The signaling mechanism of the box shown in Fig. 327 is operated by the fall- 
ing of weight w; av being first raised by the depression of the left end of lever h'. 
This lever is depressed as follows : When the inner door of the box is shut a starting 

FIG. 326, 




SIMPLE FIRE ALARM CIRCUIT. 



hook H, wliicli extends to the front of the inner door, is placed directly over the end 
of h', in such a manner that when the hook is pulled down from the outside of the 
inner box, the weight is raised. The weight in falling is caused to operate the break- 
wheel, as a recoil spring would do. The object in using the weight has been to 
avoid the delays and annoyance due to the breaking of springs, but recoil springs 
are now used almost exclusively. 

Each signal box is provided with a '• testing " switch, a lightning arrester, and a 
signaling key (shown at the bottom of the box) by means of which an inspector 
may communicate from the box to the central office. Each box. is also equipped with 
a small electric bell, or gong, as g, in Fig. 327, npon which the strokes of the alarm 
are heard. This serves two purposes. It notifies the one giving the alarm, that the 
signal has been transmitted properly and it also warns others who may have opened 
another box elsewhere, for the purpose of sending in another alarm that a prior 
alarm is in process of transmission over the circuit. The electrical connections within 
the box are, as a rule, so arranged that v/hen the outer door is closed the gong mag- 
nets are cut out of the circuit. The advisability of this will be obvious when it is 
considered that there might be 15 or 25 such magnets in a circuit, the combined re- 



FIRE ALARM TELEGRAPHY. 



439 



sistance of whicli would, otherwise, be unnecessarily added to the circuit, llie electrical 
connections of this signal box will be shown more in detail in subsequent diagrams. 

What has been thu8 far said relates almost entirely to the sending in of alarms 
to a central office; and the simplest apparatus required for the reception of an alarm 
has been shown in Fig. 326. 

Much more than this, however, is generally used in practice. For instance, it is 
desirable that a record be made of the alarm received, and for this purpose recording de- 
vices are provided. Again, 



FIG. 327. 



in the large cities, 



the 




FIRE ALARM STRKET BOX, 



number of signal boxes 
is greater than is deemed 
advisable to place on one 
circuit and, therefore, a 
number of separate cir- 
cuits emanate from the 
central office. This neces- 
sitates the employment 
of devices to repeat alarms 
received on any one circuit 
Dver all of the other cir- 
cuits. These repeaters may 
be either manual or au- 
tomatic. 

When tower bells or 
cliurch bells are rung from 
tlie central office on inde- 
pendent circuits, special 
a])paratus is furnished for 
the purpose. 

In the later forms of improved fire alarm signal boxes the spring is wound up aftei 
the manner of a clock-spring and the mechanism is started by simply pressing a but- 
ton, or by pulling upon a hook. 

Also the break-wheel, in improved boxes, is caused to revolve four times, instead 
of once, as formerly. This is done in case the firemen should mistake the first 'round ''; 
or lest an accidental grounding of the circuit should momentarily confuse the signals, 
eUi. The recoil springs are capable, when fully wound u)), of sending in forty or 
more alarms, and an index is placed in each box to indicate- to the inspectors, or others 
having access to the box, the total number of "rounds" sent in, and the need or 
otherwisf of re-winding the spring. 

Fxperience has shown that it rarely happens that two fire alarms from different 
boxes are started over the same circuit at exactly the same time. The result of such 
an occurrence would, of course, be to confuse the signals. 

In order, however, to minimize the chances of such an occurrence, ninny devices 
designed to preclude the sending in of an alarm from one box while an alanu is being 
transmitted from some other box, have been introduced into the boxes. Boxes equip- 
ped with such devices are termed " non-interfering" boxes. 



440 



AMERICAN TELEGRAPHY. 



It is often thought desirable also to extend city fire alarm circuits to buildings, 
factories, etc., without, at the same time, clogging up the main circuits with addition- 
al mao-nets, break-wheels, etc., and without running the main circuit into comparative- 
ly inaccessible places where line " troubles ' ' might be frequent and difficult of repair. 
To effect the desired result with the minimum of complications to the main circuit, a 
number of different arrangements, consisting of auxiliary box connections, and of cir- 
cuits extended from the regular street signal boxes, have been devised. 

Illu?trations of boxes and diagrams of circuits in which these improvements have 
been introduced will be found in the succeeding pages together with detailed descrip- 
tions of the same. 



The Gamev\^ell Fire Alar^i Telegraph System. 

The " main " alarm circuit of this system includes the usual street signal boxes 
and central office apparatus. 

The central office apparatus consists essentially of a relay in each circuit, a "mul- 
tiple pen, " or other form of register, for each relay, to record the alarms as received, 
and an automatic or manual repeater by which signals received on any one circuit are 
repeated over all of the others. 

In the most improved rejjeating apparatus for central offices of the Gamewell 
system an alarm received on an^^ one circuit is automatically repeated over all the 
other circuits, and, to prevent interference with the repetition of those signals, by 
incoming signals on any one or more of the other circuits, suitable mechanism is pro- 
vided. The apparatus by means of which this is accomplished is termed a non-inter- 
fering automatic repeater. 

THE GAMEWELL AUTOMATIC NON-IXTERFERING REPEATER. 

This repeater, as arranged for three circuits is illustrated in Fig. 328. 

The repeater is provided with '' locking " mechanism whereby all the armatures 
of the relays of the different signal box circuits, excepting the one on which the alarm 
has originated, are " locked, " and are thereby prevented from responding to any 
new alarm that may be started, or from sending in confusing signals (due, perhaps, to 
accidental breaks of the wires, crosses, etc.,) during tlie transmission of an alarm. 
One of the features of this repeater is that no local batteries are needed in connection 
with it. 

In Fig. 328, Ri, Ro, R3, are the relays of the fire alarm circuits. w',w' are wires 
leading to contact strips resting on an insulated cylinder at c, on certain parts of 
which cylinder are placed metal segments m, (^^hown separately in Fig. 329.) , The 
trains of wheels, etc., on the left, are operated by the weights w,w,w. s is a shaft, 
geared by means of beveled wheels bw, Avith one train of wheels. This shaft carries 
downward-hanging rods ry^i\^,r^. These rods are loosely mounted on eccentrics at 
e^e, which latter are rigidly attached to shaft s. When that shaft is given a partial turn 
the eccentrics push the rods downwards. At the next half turn of the shaft the rods 
are restored to their original positions. These rods assist in locking the armature 



THE GAMEWELL AUTOMAllC REPEATER. 



441 



levers of the relays and in repeating the signals to the various circuits, in a manner 
described later. The shaft ls carries rods /, /, /, rigidly mounted upon it,and standing, 
normally, upright. A long hinged rod R is also mounted on shaft ls. 

R is loosely hinged at its upper end/ to a lever /', (Fig. 329.) On the end of lever 
/' a pin sp engages with an arm a, which latter, when released, permits cylinder c to 
make one revohition, and the shaft s, on which rods r,r,r, are loosely mounted, a por- 
tion of a revolution. 

FIG. 328. 




GAMEWELL AUTOMATIC FIRE ALARM REPEATER. 

With this general allusion to the apparatus shown in Fig. 328, reference^ will 
now be had to Fig. 329 which is a side view of 07ie of the relays rS its armature lever, 
etc., and rods r and /, etc. 

The lever 11 is furnished with a counter poise c\v which just over-balances that 
portion of tlie lever to the right of tlie trunnion x. The armature lever a, of r', is 
pivoted at x and, owing to its closeness to the core of r^, it withstands a very strong 
pull of the retractile spring rs. In Fig. 329, /, ls, r, s and e correspond to parts sim- 
ilarly lettered in Fig, 328; it being understood that in Fig 329 the shafts s and ls 
are shown in cross-section. The rod r is equipped with a weight, CP, whicli gives its 
lower end a slight tendency to the left. This brings the angular extension at its lower 
end loosely aoainst lever a. 



442 



AMERICAN TELEGRAPHY. 



A pin /' projects from one side of r, virtually as indicated. When the arma- 
liire lever a is attracted, all the circuits being closed, this pin projects a short distance 
above the flat spring fs, as in figure. The lever h extends out to the rod r. Nor- 
mally the right end, or tip, of h is just under the break b in r. Fig. 329 represents the 
position of the levers, armatures, rods, etc., of all the relays, when at rest. 

FIG. 329. 




C>A\\VVV>A\VVVVVVVVVAAAWVVV\,VV\WVV\\VVVW5; 



GAMEWELL AUTOMATIC REPEATER, TH fSORV. 

It may be seen that the main circuit in Fig. 329, after passing through the relay, 
passes to the flat strip fs, thence to another flat strip fs' which rests against fs, and 
thence out to the line again, as indicated by the arrows. Two short wires w', w', 
lead from the flat springs /j,/j-', to two flat springs cs, cs\ which rest, normally, on 
an insulated portion of the cylinder c, in such a manner that the short circuit via 
wires w,w', is usually open, m' on this cylinder is a short metallic strip, curved to 
conform to the surface of the cylinder. All of the relays are similarly provided with 
short wires w'w', which are led to separate strips resting on cylinder c, and opposite 
each pair of such strips is placed, on the cylinder, a similarly curved metal strip m. 
The different strips :m m are insulated from each otlier. 



THE GAMEWELL AUTOMATIC REPEATER. 



443 



FIG. 330. 



Assuming that an alarm is now to be sent over the circuit in which relay r^^ is placed, 
Fig. 329. 

The first breaking of the circuit permits armature lever a to fall back. The lat- 
ter, in falling back, throws aside the rod r and the rod /. The rod r simply turns to 
the right on its eccentric (?,but the rod / turns also the shaft ls. This movement of 
Ls, b}^ actuating the long rod k removes the pin sp from the path of the arm a, and 
thus, by means of mechanism not seen in Fig. 329, permits the shaft s to make a por- 
tion of a revolution; and the cylinder c to make one revolution. Tlie same mechanism 
likewise causes the cam c', which is mounted on the same shaft as c, to quickly de- 
press the lever /' by contact with the roller/-'. The depression of lever/' places the 
pin sp again in the patli of arm a^ and also, at once, by the medium of long rod r, 
resets the rod / on the shaft ls, thus pushing back the armature lever a of relay r' to 
its magnet. 

It is this mechanical assistance 
extended to the return of the 
armature which allows the 
employment of the strong re- 
tractile S])ring RS on the arma- 
ture lever, for, without this 
assistance, the magnetic strength 
of the relay would not serve to 
attract its armature when the 
latter had fallen back sufficient- 
ly to throw aside the lever / 
and rod r. 

The act of turning the shaft 
s causes the eccentrics to 
quickly lower all the rods r, 

and, excepting that of relay r^, each rod engigas with the tip of lever h of its respective 
relay and depresses that lever, as shown in the case of R2, Fig. 330. This depression of 
lever n puts each detent d\\\ the path of each armature lever a, thus " locking "it, also 
as in Fig. 330. At the same time the lowering of rod r has engaged its pin/' with 
the flat strip fs and has separated it from fs\ thereby oi)ening the main circuit. This 
act, being dujilicated at all of the relays, of course, opens all the main circuits (^excepting, 
as before, the circuit of relay r') -aX^Js fs' . The next instant, however, the cylinder c, 
in the act of revolving, brings the various flat strij)s, cs^cs' ^ over their respective c.irved 
metal strij)S m, thus closing the circuits for a short time, and making a stroke on all 
of the gongs, etc., on the various circuits. The gongs, etc., on the circuit of relay r' 
will, of course, already have been operated by the break caused by the street box in 
sending in its alarm. 

The cam c', Fig. 329, as just said, at once returns the pin sp into the path of arm 
a, checking the motion of the cylinder at the end of its revolution; but the shaft s re- 
mains as first placed, namely with its revolution incomplete, and with the rods /* all 
lowered, until the completion of the alarm, and for the space of about fifteen sec- 
onds thereafter, by which time self-setting mL'chanism,outlined at tlie loft of Fig. 32S, 




c>A^A^wwvv\^vwvww\^vw 



444 



AMERICAN TELEGRAPHY. 



FIG- 331. 



permits a detent lever to fall into a slot, thus enabling the shaft s to complete its 
revolutiou and at the same time to lift tlie rods r away from levers 11 and from the flat 
springs/^, thereby allowing /i- and/^^' to come together, closing all of the circuits as 

before. 

In the case of relay rS (which we have assumed to be in the circuit where the 
alarm has originated,) since its armature a had moved before the rod r had received 
its downward motion, there was nothing to stop its normal backward motion, the re- 
suit being that its rod r is thrown to the right, out of the way of the strip fs and the 

tip of lever h, and, when, the 
next instant, r is lowered, it falls 
to tlie position shown in Fig. 331, 
which, it is seen, leaves the flat 
springs /^',/j'' intact, and leaves the 
catch d on k-ver h out of the patii 
of armature lever a. Consequently, 
that lever is left free to continue 
its back and forth motions in re- 
sponse to the makes and breaks of 
the break wheel in the signal box, 
striking, at each backward motion, 
the upright rod / which, as we 
have seen, by turning shaft ls, re- 
leases the arm a of the cam c', thus allowing the cylinder c to make one rcA-olution 
for each break of the circuit, for the purpose mentioned. 

In the event of a wire of any of the circuits breaking, the armature of the relay of 
that circuit will be released. This will cause one " stroke " to be sent over all of the 
otlier circuits. Simultaneously all of the other relays are " locked," as described. In 
the course of a few seconds, however, the mechanism of the shaft s unlocks the arma- 
tures of the other relays and thus leaves the unbroken circuits free to send in signals 
regardless of the broken circuit ; the armature of whose relay simply rests on its rod / 
until it is again attracted by its magnet when the circuit is repaired. The advantage 
of this arrangement is that in the absence of attendants none but the broken circuit 
is affected. To insure the prompt " locking " of the armature levers, the rod r is as- 
sisted by a cam k over each lever, h, which descends on the levers concurrently with 
the first partial rotation of the shaft s; the mechanism for the operation of this cam it 
is not deemed requisite to show. 

In addition to the apparatus described in connection with this automatic repeater, 
an annunciator is so placed with regard to each relay that the opening of its circuit 
lets the " drop " fall, disclosing the number of the circuit. A glance at the repeater 
thus shows on which circuit the "break" has occurred, whether ft be due to a regular 
alarm or to a broken wire. 




QVWVAAAAWVVVVVVVVVVVVVVVVWWWUAW 



NOX-INTERFERIXG STREET SIGNAL BOX. 



Fig. 332 is a theoretical diagram of a Gamewell fire alarm signal box, in which 
a four " round '' break-wheel and a non-interfering device are employed; there are also 



GAMEWELL NON-INTERFERING BOX. 445 

shown in the same figure the connections for an auxiliary fire alarm attachment and, 
at the right, an "auxiliary" alarm box. 

In Fig. 332, SB is a street signal box, with both doors removed, and the frame of 
which is indicated by dotted lines, m is the electro-magnet which actuates the non-in- 
terfering apparatus, bw is the four-round break-wheel, s is the recoil spring, or motor, 
which drives the signaling mechanism, w and w' are wheels, suitably geared with the 
motor shaft, l is a lever, pivoted at x, which lever,in conjunction with wheels w and w', 
performs an important part in causing the starting and stopping of the break-wheel. 

BW, s, w,w', M, and the clock-work gearing, are contained within a small circular 
case with a glass cover, am is the auxiliary magnet which, through the medium of 
the apparatus a and the rod r, releases the break- wheel bw when a signal is sent in 
from the auxiliary box. gm on the upper right corner of SB is the signaling gong 
or bell, already mentioned. Switch h and wires i and 2 form a short-circuit around 
the gong bell magnet when the outer door of the box SB is closed, thus cutting out 
that instrument. In the figure switch h is open, h' is a switch devised to cut off 
the auxiliary circuit when it is in trouble. This is done by throwing h' to the left, 
when the auxiliary circuit will be opened ataa'; at the same time the regular circuit 
will be preserved intact through metal strip l>. h' is moved by the ebonite cross-piece 
E. T and t' are the auxiliary box terminals. The strap-key sk' to the right of t is for 
signaling on the auxiliary circuit, r, f and sk are the cut outs, lightning arresters 
and signaling key ordinarily employed in such boxes. 

The main circuit from the central office CO, as indicated by arrows, enters SB at 
the post f', passes through the key sk and magnet gm, to the binding post bp; to and 
through the contact springs cs, to the post bp' ; thence to and through the auxiliary 
box AB; back to h' in SB; thence to the post f' and back to the central office. The 
circuit has not been traced through the auxiliary magnet am because it is shunted out 
by the auxiliary box wires; consequently, that magnet is normally "open.'' The 
manner in which this magnet is caused to operate the alarm apparatus in SB will be 
described further on. 

The non-interfering apparatus, the general principle of which is shown in Fig. 
332, is known as the "Gardiner." It consists of the electro-magnet m and its arma- 
ture lever si. The lever si is hollow at its lower end and in the tube a rod ni is in- 
serted. The rod ni is held out by a small spiral spring, as shown, but may be readily 
pushed further into the tube. 

To NI is attached a fiat brass disc d about f inch in diameter. Normally, this disc 
has a portion of its surface /^«<^<?r the pivoted bar l and an equal portion over one 
end of the starting hook, or lever, sh, the end of which only is shown in the figure, by 
a dotted square. This lever sh does not extend under the lever l. Its other end ter- 
minates in a hook outside of the inner door of the signal box. The lever sh is so 
pivoted that when the hook outside the box is pulled down the end within the 
box, is elevated. When the end sh of the lever is thus raised it comes in contact 
with the disc d which it lifts up. The disc in turn lifts the lever l up, and away from 
the pin />, on the periphery of w, permitting the train of wheels to start. This leads 
to a break in the main circuit, which demagnetizes m, whereupon its armature 
lever si is withdrawn, takinjj: with it the disc d from below the lever l. Hence the 



446 



AMERICAN TELEGRAPHY. 



U 



HlBll|l|l|l^ 




THE GAME WELL FIRE ALARM, 447 

starting hook might now he pnlled hidefinitely without bringing its end sh in contact 
with the lever l. When the outer door of a signal box is closed it thrusts a rod 
against the lever si, which rod holds that lever towards its magnet, regardless of 
whether the circuit is open or closed. When, however, the outer door is opened, 
if the circuit be then opened, as it might be, for instance, by the act of transmitting 
a signal from some other box,, the spring si at once withdraws ni and the disc d, 
away from the magnet m and out of the reach of the attracti/e force of the latter, so 
tliat it is impossible to start the train of wheels by means of the starting hook until 
the main circuit is closed and the outer door has again been closed. When the inner 
door is opened it is possible to place the lever si in its normal position by depressing 
tlie rod referred to. In the manner described, therefore, signals are prevented from 
interfering with one another. It will also be found as the description is proceeded 
with that when once any one has started an alarm signal, which is done, accord- 
ing to the directions plainly cast into the outside of the cover of the inside door, 
^ig- S33f " Pidl the hook down once and let go," it is not possible for liira to 
interfere witri tliat signal until it has been transmitted four times to the central office, 
and until he has again closcl the outer door to push the lever si. Fig. :^;^2, uj) to its 
magnet. This arrangement was rendered necessary because of the fact that people 
in their excitement would continue to pull the hook repeatedly, thus confusing the 
signal. In Fig. 333, f is the end of the rod which puslies the lever si towards its ar- 
mature by eo'.ituct with the pin f', when the outer door is closed, s is the rod 
which short-circuits the gong magnet when the cuter door is closed. 

The manner in which the four rounds of the break-wheel are obtained may novv^ 
be described. 

Referring again to Fig. 332. As already said, w', w and bw are geared up with the 
recoil spring shaft s. There is a slot s on the lower edge of lever l, and a pin j ex- 
tending from its side. On the other hand there is a pin / extending from the side of 
wheel w, and a dent ^in the circumference of w'. The dent may be assumed to be 
of the shape shown in the figure, although, to avoid complicating the drawing, the 
exact appearance of the arrangement is somewhat departed from. 

The wheel w' revolves once while w revolves twice and while bw revolves four 
times, each in the direction indicated by its arrow. When at rest pin/ is in the slot s 
and the piny is in the dent ^; the pin /, consequently, holding the train of wheels in 
check. The moment, however, that the lever l is raised the pin / moves out of the 
path of s and, for a short space, the lever is held up by the pin />, but, presently, the 
periphery of w' comes into contact with the pin/, thus keeping the lever l elevated, 
until, in the course of its revolution, the wheel w' brings the dent (/ opposite pin/, 
which act permits lever l to fall on to pm p of w, but only for a short distance when 
pin / arrives at s permitting the lever to fall to its normal place, thus again stopping 
the clock work. In the meantime the wheel w had performed two revolutions and 
BW four, with the result that the under contact spring of cs had fallen into the breaks 
on the periphery of bw, thereby opening and closing the circuit as many times and 
with as many intervals as there were breaks on the wheel; whicii breaks correspond 
with the number assigned to the box; in this ca§e 25. It will be understood that the 



448 



AMERICAN TELEGRAPHY. 



lower spring of cs recedes from the upper spring every time the former falls into the 
notches on the break- wheel. 

To the right of Fig. 332 is the auxiliary box AB. It is known as the Speicher 
auxiliary box. In that box are placed two break- wheels, aw and aw'. In practice 
they are mounted on one shaft, although shown separately in the hgnre, and they are 
operated in the same manner as is the break-wheel of the ordinary district messenger 
box. The wheel aw', in rotating, actuates its metal strips ms ms', which are in con- 




GAMEWELL FIRE ALARM BOX. 

uection with the wires leading to SB. Normally these strips are touching, thus short- 
circuiting the magnet am in SB, as stated. There are about 10 or 12 "breaks," or 
notches on the wheel aw'. As it rotates, the lower strip ms' falls into the breaks on 
the wheel and rises out of them, alternately opening and closing the auxiliary circuit 
at/o, as many times as there are breaks on the periphery of aw'. The object thereby 
sought will be explained presently. The wheel aw in rotating actuates, in a similar 
manner, its metal strips ms, ms', which strips are connected with wires leading to 
the indicator in the nearest fire-engine station. On the periphery of aw the number 
of teeth correspond to the number assigned to the particular auxiliary box, so that, 
Avhen an alarm is sent in from that box, the nearest lire station is at once apprised of 
the exact location of the lire. 

In AB a common compass, cS is placed above a small magnet m'. This magnet 
would be in the auxiliary circuit but that it is normally cut out by the short-circuit 
via c. When, however, the button v is pushed in, the contacts at c are separated 
and the main line current flows in the magnet m; which causes a deflection of the 



THE GAMEWELL FIRE ALAKM TELEGKATH. 



449 



compass c', thereby showing the person in cliarge, at the factory or other building 
in which the auxiliary box may be located, that the auxiliary circuit is intact. 

In addition to the starting hook sfi in SB, it will be observed that, if the vertical 
rod R IS raised hiirh enouofh, it will come in contact with lever l and start the clock- 
work. The lower end of R rests on the cam k. The cam is rigidly attached to the 
peculiarly shaped lever a, so that, as the right hand end of a descends the cam K 
ascends, raising, as it does so, the rod k. The end k, of a, is given an upward ten- 
dency by its spring. On the surface of a, at the right, 14 small flat spurs are set, 

FIG. 334. 




GAMEWELL GARDINER NON-INTERFERING FIRE ALARM STREET BOX, WITHOUT AUXILIARY ATTACHMENTS. 

as shown. On the lower end of the armature lever, l,' is a small cross-piece cp facing 
the spurs on a. At rest, namely when am is demagnetize (i', as, owing to the shunt 
around it, normally, it is, the lowermost spur on a rests on the cross-piece on the bot- 
tom of l'. When the magnet am is alternately opened and closed, however, fas it is 
when the break-wheel aw', in the auxiliary box, is set in motion, and the shunt around 
AM in SB is, in consequence, broken and closed at /a in AB,) one spur after 
auQther on a rests on the cross-i3iece on l' until the last but one is reached, by which time 
the cam k has lifted rod R until it has reached and raised the lever l and thus has 
started the train of clock-work. On passing the next and last spur on a, the spring 
pulls the lever a into a vertical position, which act places the '' cut awav'' edge of 
the cam opposite the lower end of rodii, whose upper end is thereby at once withdrawn 
from the vicinity of the lever l, ])y the spiral s})ring shown. The lever a then remains 
down until it is reset by an inspector of the Are department. 



450 



AMERICAN TELEGRAPHY. 



FIG. 335. 



After the usual four rounds have been sent in the lever l resumes its normal jy-- 
sitioii in readiness for another sio-nal. 

o 

The object in having the auxiliary box directly connected with the nearest fire 
engine station is that the engines in that station may proceed by the nearest pos- 
sible route to the scene of the fire, as it is evident that, in this way, valuable time 
may be saved, 

Gardiner if on-interfering box, etc.— In Fig. 334 the "Gardiner" non-inter- 
fering box of the Gamewell system is 
shown with doors open, and without the 
" Speicher " auxiliary attachment. In that 
figure CB is the gong or bell magnet, bw 
the break- wheel, ni tne non-interfering de^ 
vice, SI the knob whereby ni is reset aftei 
an alarm. 

In Fig. 335 the Gamewell fire alarm 
street signal box is shown as it appears 
with doors closed. To transmit an alarm 
the outer door is opened by a key, which 
gives access to the starting hook. 

Gamewell fire alarm indicator.— 
The indicator of the Gamewell fire alarm 
and police patrol systems is placed in very 
many of the fire engine houses and else- 
where, to give a visual recoi'd of a fire 
alarm or police wagon call corroborative of 
the strokes of the gong to be found in the 
majority of such stations. 

This indicator is illustrated in Fig. ^;^6. 

The operating mechanism is seen within 

the case Tlie number of the box whence the alarm originated is presented at small 

ivindows in the door of the indicator case. An electro-mechanical gong is shown oa 

;he top of the case. ' 

In Fig. 337 so much of the mechanism of the indicator as may be necessary to 
show the principle of its operation is outlined, em is an electro-m ignet in the fire 
alarm or other circuit. c,Cj^,C2, represent three cylinders on eacli of which num- 
erals from o to 9 are imprinted, one above the other, as outlined. Each cylinder is 
given a tendency to turn on its axle in the direction of the arrow, but is prevented 
from so doing by arms projecting from extension rods e, Ej^, E2, which, normally, 
engage with one of the pins p projecting from the side of the cylinders. 

The dotted lines may be supposed to represent the windows on the door of the 




case. 



When either of the fingers f, f^, Fg, is lifted momentarily it pushes back its cor- 
responding extension rod. This act moves the upper end of the extension rod out of 
the path of its projecting pin /, thus permitting the cylinder to turn the distance 
of one numeral, when the extension rod again engages with a pin and holds the cylin- 



GAMEWELL INDICATOR. 



451 



FIG. 336. 



der. Consequently, as often as any one of the fingers is lifted the corresponding cyl- 
inder is released. For instance, in the case of cylinder b, as the figure 5 is presented 
before the window, the finger f has evidently been lifted five times. 

The manner in which this figure is presented 
before tlie window will shortly be described, as 
well as the manner in which the numerals on the 
different cylinders are caused to appear. 

The mechanism seen at the left of the magnet 
EM, and the clock-work gearing (only a poition 
of which latter is seen in the figure) is held or liber- 
ated by the armature lever a of the magnet. A 
spring operates the mechanism. As shown in 
Fig. 337 the mechanism is arranged to operate in 
connection with a normally "open " circuit. The 
armature lever a of m is bent as shown. It carries 
an extension t. w is a small disc wheel on a shaft 
s'. The periphery of w is not circular, being cut away 
as shown. The left end of extension t, rests on this 

periphery for a useful purpose. On the same shaft, 

s', the arm or projection w' is also rigidly mounted. 

The gearing gives this arm a constant tendency to 

rotate in the direction of the dotted arrow; but 

it is normally checked by a pin p' on the side of the 

armature lever a'. Normally, also, the lever aa' is 

held in the position shown in the figure, by the bent 

lever k. k is mounted quite loosely on its trunnion 

/, and, when not upheld by the pin f, on the upper 

end of a', will drop. 

The rod q is pivoted on the wheel w at x. The 

upper end of q passes loosely through a pivoted 

sleeve which is carried by the 4-arm lever l. Nor- 
mally, the upper end of rod q is directly under 

finger r. l is loosely mounted on au axle x , which 

latter carries the gear wheel n whose tendency to 

rotate is in the direction indicated by the arrow- 

The 4-arm lever l moves also with this wheel, but it 

may be moved in either direction on its shaft. It 

may be held more or less firmly against wheel n by 

a flat spiing/' which latter may be tightened at will. 

It requires a closing and opening of the circuit of em to release this mechanism. 

Assuming the circuit to be at present open, the spring Rs is prevented from pullin^^ 

tne upper end of armature lever a' further to the right by the bent lever k. When, 

however, the circuit is closed, and the armat\u-e is attracted, the movement of a' to 

the left permits k to fall. Consequently, at the next opening of the circuit of in[ the 

S])ring RS pulls a' far enough to the right to move the pin/' out of the p;(h of anu 




GAMEWELL IXDICATOR. 



452 



AMERICAN TELEGRAPHY. 



w'. This releases that arm, which, with w, at once makes a revohition, with the following 
results : First, wheel w at the middle of its revolution pushes the rod q up against fin- 
ger r, thereby permitting the cylinder c to turn the distance of one figure. When w has 



completed its revolution q is in its usual position 

FIG. 337. 



Second, owing to the snail-shell 



shape of the periphery of w the 
extension t from a' is pushed 
to the left, bringing with it the 
upper end of a' also to the left. 
At the same time, a pin 
a, on the arm wj engages witli 
the lower arm of the bent lever 
K, raising the end of that lever 
into a ^^osition where it is again 
hooked by the pin /', as before. 
The same action brings the pin 
/' on A again into the path of 
arm w', hence, holding it at 
the end of its revolution. Fur- 
ther, immediately upon the re- 
lease of the arm w' tlie clock- 
work, which is self-starting, 
begins to move tlie arm i of lever 
L to theriglit, but not sufficiently 
to bring it [)ast finger f before 
the rod q strikes f ; and, fur- 

f^^'^^^^ss^^^ I^^Y llllll II lllllllllllll '""* thermore, whatever advance the 

l ^^^U ' 11 ^"^^^ ^ ^^^^ make to tlie riglit is 

'J^^^eSJ^ 7>' 11^^^ ^°^^ ^^y ^^^^' fact that, as wheel 

w performs its revolution, the 
small roller v' on the side of 
that wheel, hits the prong /i at 
the lower end of arm 3 of lever 
L and pushes it back to its 
starting point, which it is en- 
abled to do by reason of the fact 
that the lever l is, as stated, 
only held to the wheel n by friction. As long as the electro-magnet em continues 
to be opened and closed regularly the foregoing operation is repeated at each open- 
ing and closing, and hence, at each revolution of wheel w a figure will be advanced 
on the indicator. 

When, however, a longer interval occurs in the breaks of the circuit, as happens 
between the figures of a signal box " number," the mechanism of the indicator is so 
"timed" that, during that interval, the rod q is moved forward under the second 
finger f', and, thus,when the revolutions of w are resumed, the prong h is now out of 
tlie path of the pin v', while, on the other hand, the second prong Ji is now in the i)ath 




GAMEWELL INDICATOR, THEORY. 



THE GAYNOR FIRE ALARM TELEGRAPH. 



453 



of v', and, ill the same manner as before, the rod Q is held under f', and will lift np 
ih&t finger, releasing cylinder c' at each revolation of w; so long, again, as the sig- 
nals come in at regular intervals. If the box from which the signal emanates has a 
three-figure number the space between the second and third figure is suflficient to 
allow the rod Q to be brought under finger f^; which brings the prong h.^, in the 
path of pin y^ with a similar result. When the full number has been transmitted 
once the numerals making up the number are shown at the window of the indicator. 

When the first alarm has been received, the further motion of the 4-arm lever l 
is unchecked until its arm 2 reaches the pin t of armature lever a', with which it 
engages, thereby locking that lever, so that any further signals sent over the circuit 
of EM M'ill have no effect on the indicator until it has been reset for a new signal. 
This is accomplished by pulling down a rod r at the bottom of the indicator case, 
shown in Fig. T):i^(). 



The Gaynor Fire Alarm Telegraph Syste 



M. 



FIG. 33S. 



The street box of this system is shown in lig. 338. The break-wheel, actuated 
by the clock-work mechanism, transmits the number of the box in the usual manner. 
The clock-work is set in motion by 
the depression of the lever k which 
releases the rod e. The lever k is 
depressed by the act of turning 
the key to open the door, by means 
of a catch on the outer door, which, 
when pushed down, engages with 
the lever k which projects through 
the slot in the inner door. The rod 
K is geared with the clock-work 
in such a way tliat it makes but 
one revolution while the break- 
wheel makf s four. Thus, at each 
"alarm,*' the Ijox number is trans- 
mitted to the central oflfice four 
times. At the end of its revolution 
the rod r is again held by the lever 

K. 

When lever k is pulled down 
the gong-magnet m is automatically 
switched into the circuit at x^ to 
the left of rod k, by the lever a 
and h^ and when that rod resumes 
its normal position, after completing its revolution, the gong-magnet is again cut out 
of the circuit. 




GAYNOR FIRE ALARM STREET BOX. 



454 



AMERICAN TELEGRAPHY. 



FIG. 339 



^^zm 



The pointer i on dial d turns i point with each round sent in, and thus indicates the 
total number of alarms sent in and shows the inspector at a glance whether or not the 
spring needs re-winding. 

The spring is wound by means of the stem- winding apparatus shown at s w. 

A suitable lightning arrester, and means 
for cutting the box in and out of the main 
circuit, and also means for grounding the 
circuit, when desired, are provided within 
the box, at the lower left corner. 

The hand signaling key used in this 
box is shown separately in Fig. 339. The 
contact is made between the pin at the left 
and the cone-shaped j^iece of metal c. A 
spiral spring normally keeps the cone and 
pin in contact. When, however, the knob 
K is pushed upon, the contact is broken. 
The knQb,and with itthecone,may be turn- 
ed to secure new contacts, without breaking 
the circuit. 

The alarms received from the various circuits are recorded in the central office 




FIG. 340. 





by a multiple pen register ; one pen being provided for each circuit. 

In this system a manual repeater is used in the central office for the purpose of re- 
peatmg the signals received on any one circuit over all of the others. 

This repeater is shown, theoretically, in Figs. 340, 341, and 342. It consists es- 
entially of a cylinder c, Fig. 340, which may be termed a multiple break-wheel. On 



GAYNOR FIRE ALARM SYSTEM. 



455 



its surface, teeth, or iudentatious, /, t are arranged, side by side, to^correspond with the 



numbers of boxes in use ou the various circuits. This cylinder is caused to revolve 
cue or more times by the depression of a trip t, which releases the arm a controllmg 
the clock-work gearing cw. 

An end view of the cylinder and contact tongue is given ni 1^ ig 34 t- 



The spring 



FIG 341, 



c' is carried by an insulated block b to which 

is attached a handle ii, which extends outside 

of the " repeater " case, as shown in Fig. 342. 

By sliding the handle in one direction or 

another, the contact tongue is placed under 

any desired set of teeth on the cylinder. 

When the handle has been properly placed 

the clock-work is started, with the result that 

the box number corresponding to the set of . . 

teeth on the cylinder opposite the contact tongue c', is transmitted over all the circuits 

excepting the one on which the alarm has originated, which is temporardy aisconnected 

from the manual repeater. 

FIG. 342. 





GAYNOR MANUAL REPEATER. 



The electrical connections of the repeating arrangement are shown in Fig. 343. 
In this, c is the cylinder, or multiple break-wheel, shown end on. c' is the contact 
tono-ue. The tongue c normally rests on the cylinder. As thus arranged it will be ob- 
served that the cylinder controls a local circuit in which are a battery 15 and electro- 
magnet M. The armature lever of m carries a number of pairs of contact springs. 
Each pair of contacts controls a main alarm circuit — as indicated, witli batteries mu. 
Thus, as often as the multiple break- wheel circuit is opened, all of the main line cir- 
cuits will be similarly opened, in the usual manner, by the operation of the armature 
lever of m. 

The numbers shown on the rear of the repeater case, Fig. 342, represent the num- 
bers of the street boxes. The act of placing the index opposite a given number places 



45^ 



AMERICAN TELEGRAPHY. 



the contact tongue beneath the corresponding break-wheel on the cylinder within the 
case. The clock-work is tripped by pushing upon the button n. 




MANUAL REPEATING TRANSMITTER GAYNOR. 



The knobs at the right control circuits communicating with the various officers of 
the Fire department. 



Jersey City or Speicher Fire Alarm Telegraph System. 

Where tower bells are struck to announce fire alarms, unless the speed of the 
gearing of the signal boxes is much reduced, sjDCcial apparatus for regulating the speed 
of the strokes is necessary, since the box numbers can be transmitted much more rap- 
idly by means of the " break- wheels " of the street box than it is feasible to transmit 
them over a " tower bell " circuit controlling the ponderous hammers of the bell. 

Tower bells wliicli are rung in connection with the alarms from signal boxes are 
useful in at least two respects. For example, in some cities where a large regular force 
of firemen is not kept,a number of extra men are employed, subject to call, in certain 
districts. These men are attached to certain stations, but are supposed to sleep at 
their homes and to respond to the alarms of fire as sounded from the tower bells. 
Again, ic gives business men and others interested, who are furnished with a directory 
of the location of the various signal boxes, a general idea as to the nearness of a fire to 
their places of business, etc. 

A tower bell system is quite extensively employed in Jersey City, X. J. 

The apparatus of the Jersey City fire alarm telegraph system, including the 
electro-mechanical apparatus for automatically actuating the tower bell circuit, is 
shown theoretically in Fig. 344, in which r^ e^ r^ r* are relays in the signal box cir- 
cuits No. I, 2, 3 and 4. 0,0,0,0, may represent signal boxes in those circuits. b,b,b,b, 
are the main batteries for those circuits. The street boxes used are the Gamewell non- 
interfering. 

In many fire alarm systems the alarm signals received in the central office are re* 
corded by an ink recording register; the number of the box being represented on the 



SPEICHER FIRE ALARM SYSTEM. 457 

paper by so many dashes; the figures of the number being separated by a larger space 
between the dashes. In the Jersey City central office system, due to J. W. Speicher, 
the records of alarms are made by punching, in the paper tape, holes corresponding in 
number to that of the signaling box. These holes in the tape, besides acting as a per- 
manent record, are also caused to perform another function, to be presently described, 
in connection with the striking of the tower bells. 

RR is the automatic repeater by means of which an alarm received on any one of 
the signal box circuits is repeated over all of the others. In the figure, four such cir- 
cuits are indicated. c,c,c,c, at er are flat, steel strips, having platinum contacts at 
their riglit hand ends. Immediately^ above the latter are other contact points c'c'c'c', 
attached at//// to the insulated cross-piece p, of the lever l, wdiich is fulcrumed at 
K. Each of tlie circuits is caused to pass through one of the strips c and contacts c'. 
Normally, a flattened .portion of the circumference of wlieel w on shaft h, rests on the 
lever l and thus the spring s holds the contacts c' against strips c, ard hence, the cir- 
cuits remain closed at those points. By means of a weight, not shown in the figure, 
the wdieel w is given a strong tendency to rotate in tlie direction of the arrow, but, 
generally, it is prevented from revolving by the presence of the long rod lk, which 
holds in check the extended arm a which is rigidly attached to shaft h. When, how- 
ever, LR is withdrawn from the path of arm a, the wheel w rotates, and the round por- 
tion of its circumference coming in contact with the lever l, the right end of that 
lever is depressed and its left end is raised, which act opens all of the signal box cir- 
cuits at the various contacts c'. 

The right liand end of rod lr is connected with wheel w' through the medium of 
the crank- rod to which lr is hinged at f. lr is caused to slide in bearings /^, //. 
When the wdieel w is caused to make a revolution in the direction of the arrow^, the 
rod LR is momentarily withdrawn from the path of arm a of shaft h. The wheel w' 
is, itself, held in check by the contact of the arm a', which is firmly attached to w' by 
a bent extension, e, of the armature lever al of the local magnet m. On the same 
shaft, s', with w', is arranged an eccentric^ upon wdiich is mounted a hollow head h of 
a " puncher '' t. Tlie eccentric is so constructed as to give the puncher a quick down 
and up motion, through the paper tape, when the shaft s' is rotated. This shaft, like 
the shaft h, is given a strong tendency to rotate by means of a weight. 

The paper reel, ;', on which the unpunched paper tape is wound, is automatically 
started to unreel when the magnet m attracts its armature, and the clock-work is ren- 
dered self-starting and self-stoi)ping by well know^n mechanism, not shown in figure. 
Thus the magnet IM controls the entire apparatus thus far described, for, when it is at- 
tracted, the extension e of armature lever al is withdraAvn from the path of a'; this 
permits the rotation of shaft s' which causes a hole to be punched in the paper tape; 
at the same time the rotation of wheel w' withdraws lr from the path of a, allowing 
w to rotate, thereby opening all of the circuits at c', /, etc. ; and reel r starts 
to feed out the paper tape. 

The local circuit of magnet m is connected to the back contact and to the levers 
of all of the relays, so that, normally, it is open. When, however, a signal is trans- 
mitted over any one of the circuits, say, No. 3, it causes relay \\^ to open, which act 
closes the local circuit of magnet m, starting the mechanism, as just described. Pres- 



458 



AMERICAX TELEGRAPHY 




SPEICHER FIRE ALARM SYSTEM. 459 

ently the relay e^ is closed again, thus opening local circuit of m and at once arresting 
the motion of the mechanism. Thus, almost concurrently with the first break of cir- 
cuit No. 3, all of the other circuits are broken at c'/, and, in quick seccession (at tlie 
rate of about one break, per second) the breaks are received on relay R^ and repeated 
to the other circuits. In the same manner an alarm coming in over any one of the 
other circuits is transmitted over all the remaining circuits. 

It may be remarked that the wheel w' makes its revolution in much less time than 
one second, but, by a very simple escapement device attached to extension e, not seen 
in tlie figure, the wheel is arrested at the end of its revolution until the magnet m is 
again attracted. (A practically similar escapement device will be seen illustrated in 
connection with the receiver of the Essick page and line printer, d, Fig. 323). 

The '• tower ' ' circuit is seen to the right of the figure. The paper tape after being 
punched passes in a suitable guide to a ]3aper winder pr. The tape between the reel r 
and PK is held taut by means of a weight w, the handle of which, on which is fastened 
a small roller, is hung over the paper as shown. 

As already stated, the paper tape is punched at the rate of one hole per second. 
The breaks sent over the tower bell circuit are transmitted at the rate of one in two 
seconds. Consequently, the reel r is caused to feed out the tape at twice the rate at 
which PR takes it up; the surplus paper is carried down between t and wx until the 
three or four rounds of signals, as may be, have been sent in,when the reel pr gradually 
brings the weight up to its former level. The clock-work of the tower bell circuit at 
w^x is held in check by a catch, on the lower end of lever <r.r, which is brought in con- 
tact with a pin on the shaft of wx when the paper at w is almost at a level with the 
guides. There is a small counter-weight on the upper end of lever ex at v. As soon 
as the paper is started at t, the weight w begins to sink, which permits the counter- 
weight V, attached to the catch-lever ex to fall, withdrawing the lower end of ex from 
the gearing. This comprises the self-starting and self-stopping mechanism of the 
tower circuit mechanism, wx. 

The breaks on the " tower " circuit are made in a very simple fashion. The cir- 
cuit is led to a contact point c^ and to a flat contact spring/jc. Normally, these con- 
tacts are together, being held thus by the small, round, projection r on the under side 
of j(y, which projection rests on the paper tape. When, however, a hole in the paper 
passes under r it drops into it, thus opening the tower circuit at c^. It is then easy 
to see that there will be as many " breaks " of the tower bell circuit as there may have 
been holes punched in the paper. 

In this system devices have also been provided to prevent interference with an 
alarm which may have been started on any one of the circuits. These devices consist 
of mechanical attachments to the levers of the relays R^, R^, n'^, R*, controlled by a 
" locking " relay operated by an additional contact on those relays, but as in practice 
it has not been necessary to use these attachments they have not been shown in the fig- 
ure. The employment of the non-interfering signal boxes referred to practically pre- 
vents confusion of signals on any of the circuits, since, while an alarm is in progress 
over a circuit, (whether emanating from a box on that circuit, or from a box on some 
other circuit,via the repeater in the central office,) the signal box non-interfering ap- 
paratus will at once be put into operation upon the opening of the outer door. 



x6o 



AMERICAN TELEGRAPHY. 




FIG. 345.— TOWER BELL AND ELECTRO MECHANICAL STRIKLNG APPARATUS. 



FIRE ALARM TELEGRAPHY. 46 I 

TOWER BELL ELECTRO MECHANISM. 

The tower bell striking mechanism and electi'o-mechanical starting devices are 
illustrated in Fig. 345. 

In the normal position of the apparatus the hammer h' of the bell is as shown in 
figure. A bent lever cl, forming a handle for the hammer, is connected by the rod 
R, at A', with the rod r'. r^ whose trunnion f' is pivoted on framework not shown in 
%ure, carries at its other end two pawls, or dogs, d d\ which are hinged to it at hji . 
These dogs are held against, or near, the teeth of a ratchet wheel w, by a peculiarly 
curved support G, on which the pins//', projecting from the side of tlie dogs, rest. 
The object of this peculiar support will be noticed presently. The dogs are so ar- 
ranged that only one of them at a time engages with a tooth of the ratchet wheel. 
The ratchet wheel w is given a strong tendency to rotate by ponderous weights f, 
(which weigh from one ton to one ton and a half), but it is, normally, prevented 
from turning by the engagement of dog <'/ with one of its teeth, as in iigu7e. A 
pressure is, of course, constantly exerted on the rod k', giving it a downward ten- 
dency, but it is prevented from yielding to the pressure by the pin m on its side 
which rests on the pawl 11 pivoted on the side of bent lever oq. The movement of 
the pawl ;/ is limited by a pin ^, on the side of Q, in slot o'; n is normally held in its 
present position by the flat spring ;/' The bent lever oQ, which is pivoted as 
indicated at k, is provided with a strong spring s', which would pull the vertical arm 
Q into a position to the right, where the pawl n could slip from under the pin /;/ of 
rod k', but that it, oq, is held in check by a hook 11 on the lower end of a pawl r. 
r is loosely mounted on a shaft s. Thus as long as the hook a is held under the 
left end of arm o of lever oq, the ratchet wheel w will not move. 

On the same shafts with the pawl r is a bent lever l.sr one of whose arms 
L rests on a short extension ex from the top of the armature lever al of the relay 
M, which is in the tower bell circuit. The arm sr carries at its upper end, a weight a 
which gives the arm l of the lever a constant downward tendency. The extension ex, 
looked at from the top, is of a U shape. There is also an extension v from the lowei 
arm of lever l sr. These extensions are so arranged that, normally, the extension v 
rests on the outside leg of ex in such a manner that when the armature lever is re^ 
leased and is withdrawn from its magnet the extension v of l slips off ex and thus 
L has an unobstructed path in which to fall. 

On the shaft s, also, is another lever v'. Both l and v' are rigidly mounted on shaft 
s, so that when lever l falls it turns with it that shaft which, in consequence, throws the 
lower end of v' to the left. Assuming the tower bell circuit to have been broken, thus 
allowing the armature of m to fall back, the extension v of arm l is released and it falls. 
At the same time the arm v' is thrown to the left which brings it sharply against a 
pin, HP, on the side of the pawl r. This knocks the hook h from under the end of o, 
which latter then, in response to its spring s', falls. This act removes the pawl /; 
from the pin /;/, freeing the rod r'. At once the weight f acts on the dog d^ causing 
the rod r' to move dovvnwai'ds, which act causes the withdrawal of the hammer n' 
from the bell. The motion of the ratchet wheel which accompanies that act brings 
d' into sudden contact with the next tooth t and this shakes the upper dog d 



462 AMERICAN TELEGRAPHY. 

from the tooth with which it was engaged. The result is that the pressure of the 
weight is now put upon the dog </' ; the rod k' is caused to reverse its previous mo- 
tion; the hammer h' is tlirown violently against the bell, land the pawl d again en- 
gages with a tooth, as in the first place. At the same' time, and while e' is thus caused 
to rise, its pin m pushes back the pawl n until it gets above it, when the fiat spring 
n' pushes n again under pin ;/z. At the same time also, the rod k', in rising, throws 
the arm o of oq up, so that its spur g, coming in contact with the pin w, on v', raises 
that arm, and, in consequence, the arm l, so that the extension v slides above ex, (the 
latter yielding slightly), and then settles down upon it, the magnet in the meantime 
having been attracted. The arm o of oq having been raised above the hook h on 
pawl r is caught aud held as before. 

At the next and subsequent openings of the circuit the foregoing actions are re- 
peated. 

It will be seen that as dog d is moved to the right, in the figure, the pin /' gets 
above a hollow in the curve of g, while the simultaneous forward motion of d 
brings it on a ridge of the curve. Thus, in the first case, d is given room in which 
to fall clear of its tooth, while, in the second, d' is raised up into the path of its next tooth. 

It is, of course, understood that the whole process of raising the hammer and 
striking the bell is comparatively rapid, since it must be accomplished in less than 
two or two and one half seconds, which is tlie rate at which the signals are trans- 
mitted over the tower bell circuits. 

In some cities, for example, Newark, N. J., the tower bell magnets are placed in 
the signal box circuits, and the mechanism of the break-wheels in the boxes is some- 
what reduced in speed. 



The Gamewell Auxiliary Fire Alarm Telegraph. 

It has already been pointed out {^See Gamewell fire alarm telegraphy) that the ob- 
ject of an auxiliary fire alarm system is to increase the utility of the main fire alarm 
telegraph by increasing the number of places "from which alarms maybe transmitted, etc. 

The chief features of the Gamewell auxiliary system are illustrated in Fig. 346 ; 
namely, the auxiliary box and the auxiliary mechanism in the street box. It is well 
known to those concerned that, as a rule, municipal fire departments strenuously ob- 
ject to the introduction of any apparatus into the street signal boxes, or elsewhere, that 
may tend in any way to complicate or hamper the operation of the existing systems. 
To meet this objection the Gamewell auxiliary system has been designed. It avoids any 
electrical connection whatever between the auxiliary alarm circuit and that of the reg- 
ular circuits of the fire department. This being the case a special battery is obviously 
necessary in the auxiliary circuit. 

In the figure, AB ife an auxiliary box, located at any desired point of the auxiliary 
circuit. This box serves the double purpose of causing the operation of the street fire 
^larm box, and of giving an "answer back " signal, signifying that the alarm has been 
fitartfci over the reo-ular or main alarm circuit, b and b are the batteries used in con- 



THE GAMEWELL TELEGRAPH. 



46. 



section with tLe auxiliary circuit. The smaller battery b is used only for testing pur- 
poses, as will be explained. 

SB shows a portion of the street fire alarm box. bw is the usual break- wheel, am 
is the auxiliary magnet placed within SB. When this magnet's armature al is at- 
tracted the rod r is raised, lifting the lever l, and thus starting the clock-work which 
operates the break-wheel in the usual manner. 

The auxiliary box AB is provided with an accessible hook h attached to a lever l'. 
Three strips of metal 1,2, 3, insulated from each other and from the box are placed 
as shown. Normally lever l' rests on strip i. In this position of lever l', the auxiliary 

FIG. 346. 



Cl^ 




ToCe/t/rajL 



GAMEWELL AUXILIARY FIRE ALARM CIRCUITS. THEORY. 



circuit is completed through the small battery b. The current from this battery is, 
however, too weak to operate the auxiliary magnet am in the street box. When 
the lever l' in the auxiliary box is pulled down, as in case of fire, the moment it touches 
strip 2, the large battery B is brought into the auxiliary circuit. The strength of the 
current thereby added to that circuit operates the auxiliary magnet am, in the street 
box, and, in consequence, the clock-work of that box is set in motion, precisely as if 
it had been started by a pull on its own lever. 

When the lever l' at AB is still further pulled down, it makes contact with strip 
3. This, it will be seen, diverts the current of battery b through the " buzzer " z, there- 
by attracting its armature ^, and, for the moment, holding it there. Within one or 
two seconds, however, an arrangement provided in the street box, in connection with 
this auxiliary system, consisting of the projection/ attached to the break-wheel bw, 
engages with the small lever /, moving the latter away from the contact point >", and 
thus opening the auxiliary circuit at that point. The small lever / is held against 
x^ normally, by the counter poise shown. 

It being assumed that the one giving the alarm from the auxiliary box has been 
instructed to hold down the lever \I on contact 3 for a few seconds, the result is that 
the opening of the auxiliary circuit at the street box ]xn-mits the armature of the buz- 



464 



AMERICAN TF.LEGRAPHY. 



zer to spring back against a contact point x\ thus momentarily completing a circuit 
through the buzzer, battery b, strip 3, lever l' and armature a; whereupon the usual 
action of a buzzer ensues, thus announcing that the street box has been started ; for as 
we have seen, the "buzzer" z only acts as a buzzer, when the auxiliary circuit has 
been broken by the break-wheel in the street box in the act of turning to transmit its 
number over the main fire alarm circuit. This buzzer acts somewhat differently from 
the ordinary, in that, normally, it rests away from its back contact and depends for its 
start upon the rebound of its armature lever from the magnet, when the auxiliary circuit 
is broken. 



FIG. 347. 




GAMEWELL AUXILIARY FIRE ALARM.— CONNECTIONS. 



The auxiliary circuit is not only broken at the lever / in SB by the projection from 
the break- wheel b\v, but the lever is also thrown by that projection to a point where 
it remains until reset by some one duly authorized to open the street box. This, in 
addition to facilitating the transmission of the " answer back" signal, insures that 
when an alarm has been started from that circuit no other alarm shall be sent in until 
the lever / has been reset. 



In many of the buildings, such as factories, warehouses, etc., equipped with aux- 
iliary fire alarm apparatus, it is desirable that the officials of the building should be ap- 
prized, simultaneously with the giving of an alarm to tlie street box. As, also, in 
some buildings auxiliary boxes are placed on every floor and in every room, to the 
number of out hundred and more,it is evident that means must be provided at some 
suitable point in the building for testing, etc. 

In Fig. 347 apparatus and connections to effect the foregoing results are shown. 

This apparatus is generally located in the manager's or superintendent's office in 
the building. 



THE GAMEWELL TELEGRAPH. 465 

B and b are the batteries shown in Fig. 346. CR is termed the "cross " relay; 
TR the " trip " relay; ru the " fire " bell; dp. the " disturbance" bell; Rh is a rheostat 
of about 500 ohms resistance; G is a common galvanometer, or indicator; ab and ab' 
are auxiliary boxes in any desired part of the building, ab is shown with cover off 
and, enlarged, the better to show the connections. The " trip " relay tr is 
equipped with a hook lever ; insulated at the hook h. 

Normally, the auxiliary circuit is closed, as shown in Fig. 346 and in Fig. 347. 
As has ])oen said, the current from small battery b is insufficient to operate the aux- 
iliary magnet am in SB. The adjustment of the retractile spring s of te is such that 
its armatm-e is just attracted to the hook h and held against it, as in the figure, by 
battery b. The circuit in which ck is placed is normally open at switch s. The local 
circuits of the alarm bells fb and db are also normally open. 

When any one of the auxiliary boxes is pulled, the first effect, as explained, is 
to bring into the circuit the large battery b. This not only operates the auxiliary 
magnet in the street box, but also the relays ck and tr in the building; the increased 
current strength being sufficient to attract the lever of Tnpasf the insulated hook //, 
which hook at once *' locks " that lever. The effect of the attraction of those relays 
is that the local circuits of fb and db are closed, and both of those bells are caused 
to ring. 

As we have seen, the auxiliary circuit is broken at the street box within a second 
or two after the auxiliary box has been pulled. The consequence is that the relays 
TK and CK are at once demagnetized and the disturbance bell db, controlled by the 
lever of ck, stops ringing. The trip relay, however, is still held towards its armature 
by the hook //, and the fire bell continues to ring until the hook h is removed by the 
depression of a suitable knob, not shown in figure, Vhen the spring s retracts the ar- 
mature lever and (as the auxiliary circuit is now open at sb), holds it against its back 
contact point c. Hence the disturbance bell circuitis again closedby a new route, and this 
bell continues to ring until the auxiliary lever / in the street box is reset, which act 
by closing the circuit, again brings the small battery ^ into service and thus, again, 
the armature lever of te is attracted, up to the hook h. 

FIG. 348. ^^ ^^^^ galvanometer g is always in the auxiliary circuit its 

needle assumes a uniform deflection due to the small battery. Thus 
a glance at that instrument indicates the general condition of the 
circuit. Should the auxiliary circuit open by an accidental break, 
or otherwise, the trip relay falls back, operating the disturbance 
bell. Should the wires ol and cl in the building become crossed 
the relay CR- is at once attracted and again the disturbance bell 
is rung. The normally open wire ol and battery b may be 
tested by turning the switch s, at which time the presence of the 
resistance Rh, by temporarily reducing the current strength, pre- 
vents any effect being felt in the relays ck, te, or th.e magnet am, 
AUXILIARY FIRE ALARM by uuduc iucrcase of current during such tests, 

^^^' An auxiliary fire alarm box is shown in Fig. 348, as it appears 

in practice. Very frequently a small pane of glass is inserted in the frame to pro- 
vent meddling with tlie liook. When an alarm is to be transmitted tlie ghiss is broken 
to give access to the hook. 




466 



AMERICAN TELEGRAPHY, 




fire alarm telegraphy. 467 

Automatic Fire Alarm Telegraphy. 

In many of the large cities of tlie United States an auxiliary to the regular fire 
alarm system is to be found in the use of automatic fire alarm telegraph apparatus, which 
on the occurrence of fire in a building transmits a signal to a central office, 
the attendants at which either immediately send their own firemen to the building 
from whence the alarm emanates, or make a call upon the regular fire department. 

The means most frequently employed for thus automatically transmitting fire 
alarms is some form of thermostat which is so constructed that at a certain tempera- 
ture its expansion will be sufficient to complete an electric circuit, which act sets in 
motion apparatus that transmits to the central office a specified " number " of the 
building, as well as, in many cases, the number of the floor of the building on which 
the fire has originated. This system is also somewhat analogous to that of the Amer- 
can district messenger telegraph, the chief difference being that, in the latter ser- 
vice, the subscriber operates the signaling box manually, while, in the case of auto- 
matic fire alarm systems, the increased temperature due to fire causes sending in of the 
alarm. 

One such system, due to George F. Bulen is illustrated, diagramatically, in Fig. 349. 
The instruments used in this service, at the central office, A, are a call bell, 
inking register, and electro-magnet mm, whose function will be noted later ; a small 
battery b and the main battery sb ; and, at the building to be protected, BP, a trans- 
mitter, comjjrising a multiple break- wheel x; a cylinder c, partly insulated, and 
carrying raised metal segments v,v,v, on which the contact strips s, s/ s,^ s,^ s^, s^, 
normally rest, and the various electro-magnets m^, m^, m^, and other contacts and 
apparatus to be specifically described shortly. 

A metallic circuit l,l, extends from the central office A to the protected building 
BP; the same circuit is extended to every floor in the building, or to as many floors as 
may be desired; in this case being looped into the first and second floors as shown. This 
circuit is also brought to the break- wheel x at the periphery w, but, when that wheel 
is at rest, the circuit is merely continued through the metal of the periphery. This 
circuit L is grounded at the central office as indicated, but, ordinarily, it is not ground- 
ed in the protected building. In addition to the line circuit, a local circuit /,/is looped 
through every floor in the building. The local circuit, before passing to the respective 
floors, is first passed through metal strips s^s^jSj^s*. The same circuit also passes 
through the strips s^ and Sg and small local battery b', thence through the magnet 
M3 and through the armature lever and back stop of magnet Mo. Normally this cir- 
cuit is closed and, consequently, the armature of M3 is on its front stroke. When 
thus attracted the armature of Mg holds a projection from a normally, rapidly re- 
volving break-wheel bw, having notches corresponding to the designated num- 
ber of the building. A wire w from the main line at o leads to the contact spring of 
break-wheel, and the frame of the latter is connected with the earth. This 
ground circuit is open except when the break-wheel is revolved. The local circuit / 
is tapped at ^' by a wire w', which, after passing through the magnets m-m^, and 
battery b^ is connected to the earth. Ordinarily this has no effect on the local circuit /. 
The cylinder c is given a tendency to a partial rotation by a retractile spring, as 



468 AMERICAN TELEGRAPHY. 

shown, but it is prevented from making this movement as long as the projection z, at- 
tached rigidly to c, rests on the top of the lever y' of the armature of magnet m^. 
When the armature of m^ is attracted the projection z is released and the cylinder c 
performs its alloted motion. This movement of c removes the raised contact pieces 
v,v,v, on the cylinder ancJ permits the flat spring contacts s,s', etc., to fall on contact 
points p and p'. These contact points are connected to the flat spring contacts d^ 
and d2, which latter rest near, hut do not touch, certain of the peripheries of the " mul- 
tiple " break-wheel x; this break-wheel having a number of separate wheels, as 
hereafter described. The shaft of these wheels, when free to rotate, is actuated by 
clock work cw. The wheels w^w^ of x are connected metallically with the shaft x' 
of that* wheel, which shaft in turn is connected to the earth by way of the flat spring 
contact F. w^w^ carry, on their peripheries, a number of projections corresponding to 
the floor with which, as we shall presently see, they are respectively connected. "Wheel 
w has a wider periphery than w^jW^. It is furnished with breaks, or indentations, 
corresponding to the "number" of the building. These breaks on w^ are at a different 
point of its periphery than are the notches on w^,w^ or w^. The wheel w^ is a 
smaller wheel side by side with w. w and w^ are metallically connected,but are insulated 
FIG. 349 a. fi'om the common shaft x' of the multiple break-wheel. w~'= has one 
portion of its periphery raised, as shown (Fig. 349*^) so that at a 
part of its revolution it comes into contact with the flat spring contact 
^ R, which is in connection with the earth. The result is that, (when 
wheel X is rotated), during the time that tlie contact r rests on the 
raised portion of w^, the line l is placed to earth, excepting^ 
when the flat contact S])rings pJ r^ are disconnected from the 
periphery of w by the presence of the notches (seen in Fig. 349 a) 
which equal the " number " of the building. This suftices to send 
in to the central office the regular number of the building. The raised portion of w^ 
is sufficiently prolonged to permit the transmission of the building "number" at such 
times. When the raised portion of w'^ passes e the line circuit is disconnected from 
the earth at that point during the rest of the revolution of x. 

It may be seen that the main line l and the local circuit / are, at several points 
on each floor, separated from each other only by thermostats t,t,t. When, therefore, 
the temperature in any of the floors exceeds the " safe" temperature of the thermostat, 
the space by which the two circuits are separated is closed, and thus they are elec- 
trically thrown together; it is then the function of the transmitting apparatus to 
communicate to the central ofiice, not only the building number, but the floor in the 
building on which this has occurred ; and this it does in the following manner : 

Suppose that this connection takes place at t' on the second floor. The result is 
that the current from the main battery sb at central station A passes from the line 
wire L to the local circuit wire /, and through the flat contact strips s* and s^ to ^ mag- 
nets m^,jm2,m^ and earth. This curient has the effect of attracting the armatures of 
the magnets M^^M^jbut the most important work is performed by m^, which withdraws 
the catch y' from arm z. This permits the spring to draw down the arm z, thus partly 
turning the cylinder c. This movement of c releases the catch y attached to the 
fly-wheel of the multiple break-wheel x, which latter starts to rotate (in response to 




AUTOMATIC FIRE ALARM TELEGRAPHY. 469 

the cloek-work spring with which its shaft x' is geared), in the direction indicated hy 
the arrow, Fig. 349^. The same action of the cylinder c which released the catch y, 
holding the break-wheel x, permitted the flat contact springs s^,s2,s^,s* connected with 
the floor local circnit /,/, to drop dow^n on the contact points p,p, connected by wires 
with the flat contact springs resting near the break-wheel x. This now pnts the flat 
contact spring D^ in contact with the line wire l, via the local wire at contact t' on 
the second floor. Contacts s,s^, also drop on snitable stops. 

Assuming now that the break-wheel x has started to rotate. Presently the contact 
K touches the raised portion of w^. This completes a main line 'Aground" circuit via the 
periphery w and contacts r^r2 ; the next moment the contacts r^r^ come opposite a 
notch in the periphery, "opening" the line l again, and this is repeated, say 4 times, 
assuming that to be the " number '* assigned to the l)uilding. This indicates, both 
on the bell and register at the central oflice that an alarm is in from building 4. Ilav- 
ino- sent in this signal the main line is momentarily open, but, as the break-wheel x 
rotates still further, the raised points on the periphery of Wo meet flat spring contact 
D^ and close the "ground" circuit twice in succession, via the thermostat at t', thusindi- 
catinof to the central office that the alarm lias orio-inated on the second floor of buildino- 
4. The actuating clock-spring of break-wheel x is wound sufficiently to cause tliat 
wheel to perform a immber of revolutions : consequently, the building number and 
floor number are sent in, over and over, until the spring runs down. 

If it should be desired to protect more than two floors it is only necessary to add 
the necessary segments and flat springs on cylinder c, and peripheries on the multiple 
break- wheel x, to meet the requirements. 

In order to insure the 2)roper Avorking of tlie line and local circuits at all times, 
and to prevent false alarms of fire, it is necessary, when either of those circuits " open '' 
or "ground " from any cause, other than the operation of the thermostat, that a dis- 
tinoruishiuo- sio-n or sio'iial, should be forthcomino'. 

It is the office of the electro-magnet mm and tlie small battery b, at A, and 
that of the electro-magnets M^, and M^, and the small break- wheel bw, at the pro- 
tected building, to " announce " such oj^ens, or breaks, which they do as follows: 

As already said, the local circuit / in BP is normally closed; hence m^ is mag- 
netized and its armature is attracted. Assuming the circuit / to be, in some way, 
broken, the armature of m^ falls back, thus releasing the " fan " of the small break- 
wheel BW, which rotates rapidly, grounding the main line repeatedly, and " sending " 
the number of the building over the main line. This indicates to the central office 
that there is a defect in that building in the local circuit. 

If, on the other hand, the local circuit /should become grounded at any point, a 
short-circuit is formed from that ground, through m^m^, short wire w' and the small 
battery b^ to the ground. This battery is not strong enough to attract the armature 
of M^, but does attract that of m? This opens the local circuit / at the back stop of /^ 
of M-, also with the result of releasing the fly which holds the clock-work of the 
small break- wheel, and again the building number is transmitted to the central office. 

If the line wire l should open, the effect is to demagnetize the electro-maoniet, 
or relay, mm, at A, that instrument being in a metallic circuit. Or, if either of t 
\ine wires forming the metallic circuit should ground, it will be announced by a clos 
ing of the bell magnet and register in the central office. 



lie 



470 AMERICAN TELEGRAPHY. 

In practice tlie building numbers are recorded by an ink register, as dashes, the 
floor numbers, as dots. Thus a signal from building 4, floor 2, would be recorded 
on the paper as ■ • • This is due to a greater length of contact on wheel w. 

Self-starting and self -stopping registers are used in this service. 

Reverting to Fig. 349, when an inspector in making his tour of the circuit de- 
sires to announce his presence at a certain building he simply pushes in the plunger k. 
This, it will be seen, first closes the dotted line circuit at cp and then removes the ar- 
mature lever y' of m' from the path of the catch z which allows the cylinder to turn ; 
this, in turn, releasing the break-wheel x, which also turns. The first action of the 
break-wheel is to send in the building number, as before, and afterwards to mnke 
contact with flat strip d^ which then causes a series of 2 makes and breaks of the 
main line circuit, which is evidence that the signal has been sent by the inspector. 

The form of thermostat, T, Fig. 349 h used in this system consists of a bi-metallic 

sprino^ which is bent normally into the shape of a 

FIG. 349 Z-. i O T T . IP 1 

crescent, one end being securely fastened to a 
standard, while, oj^posite its free end, a platinum 
point P is adjusted. The spring is made of 
steel and copper. The more expansive of the 
two metals under heat, namely copper, is on the 
outside of the spring. Wlien tlie spring is sub- 
jected to heat it tends to coil into a smaller cres- 
cent. The coiling is soon retarded by the plati- 
num point, which completes the circuit between 
the local and main line circuits, as previously 
stated. The coil is normally adjusted for a temperature of about 130 F. 
In some systems, easily fusible alloys are employed as thermostats. 
In some systems also, two thermostats are used, conjointly, in a circuit, or in two 
circuits; one being arranged to originate an alarm slightly in adv;» nee of the other; 
this to prevent false alarms that may be due to accidental contacts between the ter- 
minals of a thermostat. 

Other forms of thermostats consist of a flat box containing substances which ex- 
pand readily under increased temperature and thus " bulge " out the sides of the box^ 
which action is caused to close or open a circuit. 




Bl-METALLIC THERMOSTAT. 



CHAPTER XXIX. 

POLICE SIGNAL TELEGRAPPI SYSTEMS. 

It lias been said, perhaps truthfully, that iu no other department of municipal gov- 
ernment, has there been so little progress as in the police department; "for the old sys- 
tem, coming down from the time when watchmen patrolled the streets with lantern, 
bill-hook and rattle, has been substantially followed." The policeman, after leaving 
headquarters with the platoon, to go upon his beat, has been free to exercise his own 
will, virtually unseen, and often out of reach. And, while this state of affairs may 
have been satisfactory, in some respects, to the policeman, it also had its drawbacks in 
that it frequently left him at the mercy of any quickly gathered mob, without ready 
means of obtaining assistance. In cases of accident also, the means at hand for speedy 
assistance from the jDolice were lacking. 

The fact that, as in the Fire department service, electricity could be successfully 
utilized as an ally in the j^olice service has, of course, long been recognized by the 
proper authorities of many municipalities, but until within the past few years no 
very general active measures were adopted to avail of that fact. 

At the present time, however, many of the cities of this country have introduced 
electric signaling systems which have, admittedly, much increased the efficiency of 
the police force. 

In the oj^eration of these systems, electric signal boxes, connected by a wire with 
headquarters, are located at stated points along the routes of the police. In some 
cases the boxes are simply placed against an available wall, or in a niche provided in 
a lamp post. In others, specially constructed houses, or booths, somewhat similar to 
" sentry boxes,'' are placed on the curbs or the corners of streets, and in these the 
signal boxes are placed. 

Each signal box is provided with a telephone by means of which the policeman 
can communicate with headquarters, and in some systems that instrument is used 
nearly exclusively, the policeman as he arrives at the signal box sending in a signal 
which intimates to the attendant at headquarters the number of the box at which 
he has arrived, whereupon the attendant communicates with the policeman 
and takes his name; thus getting a record of the movements of the policeman at each 
section of his route. 

In other systems when the policeman merely wishes to announce his arrival at 
a certain point he opens the box with a specially constructed key which sends in the 
number of the box. This number is recorded automatically on a slip of pa}>er and 
the time of receipt of the signal is automatically stamped on the same slip ; thus 
showing that the officer has been at that part of his route at a given time. If the 
])oliceman desires to send in a special signal of any kind, as for an ambulance or. 
wagon, or to obtain assistance to quell a disturbance, etc., he can do so by the use of 

471 



47^ AxMERICAN TELEGRAPHY 

a special arrangement within the box. If, on the other liand, lieadquarters wishes to 
communicate with the officer, the apparatus is set in such a way that an intimation to 
that effect will be given to the policeman, when he opens the signal box, whereupon 
he brings the talephone into requisition; or, if the policeman should desire 
to confer with the attendant at headquarters, he can^ by a pre-arranged signal 
notify the former over the wire to that effect. All of this service is performed over 
one wire in manner to be described. 

Again, in some cities, keys for the signal boxes are given to citizens, watch- 
men, etc., who are empowered to send in signals for police assistance in cases of 
emergency, and thus the jjolice force is practically augmented by a volunteer service. 
In order that the use of the keys in such hands should not be abused, the keys fur- 
nished to citizens are numbered and the " citizen's " lock of the box is so constructed 
that the key, having once been inserted in the key-hole, and turn 3d to send in a sig- 
nal, cannot be withdrawn until a policeman arrives and releases it. In this way the 
user of the key is identified. 



The Gamewell Police Signal Telegraph System. 

The police signal S3^stem of this comj^any affords facilities for the sending of a'n 
ordinary j^atrol signal by the policeman on his " beat," or special signals for ambulance; 
assistance, etc. Means for telegraphic or telephonic communication between the sig- 
nal, or patrol box, and the central office, or police headquarters, and vice versa, are also 
supplied. The apparatus and electrical connections employed to effect these results 
are shown theoretically in Figs. 350, 351. 

In Fig. 350 SB is the signal box. CO is the central office. The arrangement 
by which •' on duty" and special signals are transmitted from the signal box is a 
modification of the "Field and Firman'' electric call box. In SB, bw is the break- 
wheel, carrying only the " number " of the box on its periphery, sw is a wheel 
which is only actuated when a special signal is to be sent in. When the latter wheel 
is moved around, a roller, carried by a lever r, rides in and out of the notches n in 
the periphery, separating the contacts c/ . It Avill be seen that, normally, these con- 
tact points c^c' are short-circuited by wire w and flat spring s' which rests on a pin/ 
projecting from one side of bw. p is a pointer rigidly attached to the shaft of sw. 
When the pointer is opposite the numeral i the " on duty " call only is sent in. 
That is, the crank lever controlling bw is merely j^uUed and let go. This allows the 
break-wheel to make one revolution, in the course of which it sends in the box " num- 
ber." This number arrives at the central office and operates the relay k, in whose 
local circuit, controlled by lever l\ is a register kg. This register is provided with 
chemically prepared paper which records the number of the box as received. If the 
central office should desire to speak to the policemen sending in an " on duty " sig- 
nal, the double contact key dk is depressed. The key is so arranged that when it is 
thus depressed it first closes a circuit around the relay e and battery b, and tlien 



THE GAMEWELL POLICE SIGNAL SYSTEM. 



47. 




474 AMERICAN TELEGRAPHY. 

opens the main circuit, which actuates the call bell in the signal box. The act of 
forming a new circuit around the relay R avoids operating the register uselessly 
while the policeman is being signaled. Upon hearing the bell, after sending in an 
<'on duty "' signal, the telephone is used ; or the strap key sk may be operated accord- 
ing to a pre-arranged code. 

The telephone is showm in outline as t' in CO and t in SB. The telephone is con- 
nected with the earth, through a condenser c,c', to avoid grounding the main circuit. 
At central office the telephonic apparatus is connected with the index of a switch sw, 
by means of which it may readily be placed in connection with any of the main cir- 
cuits or with the stable s, Fig. 352. The only connection shown in Fig. 350 is with 
circuit No. i. When a policeman, or a citizen furnished with a key, desires to send 
in the signal for an ambulance wagon, fire, riot, or any other special call provided for 
among the number of special calls, he moves the pointer to the desired number and 
pulls the crank. The action of moving the pointer to the left brings in one or more of 
the cogs on the under side of sw, into the path of the cogs on the under side of bw, 
in the manner described in the explanation of the operation of the "Field and Firman" 
electric call box. The result is as follows: In the first place the act of turning the 
pointer to the left, although it opens the contacts cc' as the rod r rides over the 
teeth n^n of sw, does not break the main circuit, which still remains closed via. the 
short wire z£/ and the pin / on b w. When, however, the wheel bw begins to make 
its revolution, the flat spring s' slips off pin/, opening the wire w. Presently the 
cogs G on BW engage with the cogs g' and cause sw to resume its normal positior , in 
doing which the rod r retraces its motion over the teeth 7in^ opening the contacts cc' 
and, this time, opening the main line. The openings of the circuit, thus produced, are 
made at a comparatively low rate of speed and appear on the chemical paper in the 
central office as dashes. These are soon followed by the signals due to the passage 
of the contact h over the notches in the periphery of the break-wheel, wliich repre- 
sent on the chemical paper the "number" of the signal box from which the call em- 
anates. In this instance 51. It should be said, however, that these police signals are 
transmitted and received at a very high rate of speed by the apparatus employed — 
much more so than those of fire alarm signals, which is explainable by the fact 
that in the police system no heavy gongs are operated, as is the case in fire alarm 
systems. An electric " time '' stamp, placed over the paper tape in the central office, 
is at the same time actuated, and the hour at which the signal has been received is re- 
corded. This time stamp, it may be noted, records the time of the receipt of simple 
'•' on duty" calls as w^ell as special calls. 

A specimen of a special call, with the time stamp, is shown in Fig. 351, in which 
the four dashes represent the special call and the shorter dashes the box nLimber 51. 

When a simple '' on duty,'' call is sent in, it is, as stated, automatically recorded 
on the chemical paper, and it is not necessary that an attendant should be on tl e 
alert to receive it at the central office. — nor, unless the attendant has noticed the whirr 
of the register, need he be aware of the arrival of such a signal. It is different, 
however, when a " special " signal is sent in, as when the officer, for any reason, 
washes to arrest the attention of those in the central office. In that case the act of 
moving the pointer inSBbrings an insulated block momentarily against the contact spring 



THE 5am E WELL POLICE SIGNAL SYSTEM. 



475 



POLICE DEPT 

THE GAMEWELL 
F.A.TEL. CO. 



JUN25 72 47 AM 89 
NEW YORK 



cs, bringing that spring into contact with fs. This momentarily grounds the main circuit 
in SB at e. As, however, there is, at present, no other ground on the circuit, this has no 
effect. When the wheel sw opens the main circuit, as fig. 351. 

just described, the relay r is opened. [That relay carries 
two levers on its armature, insulated from each other. 
A branch circuit be from the main circuit at x passes via 
the lever /of R.] In returning to its normal position the 
insulated block momentarily presses again, cs against fs. 
The moment that this happens a circuit from the ground 
at E, to the ground e' in the central office is formed, through 
the relay e', which magnetizes that relay. The attraction 
of the armature a which normally holds up a lever a' , re- 
leases the latter, which falls on the contact y^ thereby clos- 
ing a local circuit through a bell magnet tb, whicli rings 
out an alarm calling attention to an incoming special sig- 
nal, the nature of which is then seen by reference to the 
record. In falling on the contact / the lever a' separates 
f»"om the lever a, thus removing the ground from the 
main circuit at x. The central office attendant resets the 
lever a' . 

When a special signal requiring the attendance of a 
wagon at a certain box, has been received, the appar- 
atus, shown as connecting the central office with the 
stable, in Fig. 352, is employed. 

The galvanometer g in the central office CO, is always 
in the main line and indicates, by the deflection of its 
needle, the general condition of the circuit, and the 
strength of current. The galvanometer tg, by the turning 
of the switch s, will indicate the side of the circuit on 
which a ground may have occurred. 

In Fig. 352 the stable electrical outfit is shown at S. 
The apparatus at the central office consists of a double con- 
tact key k; a call bell cb; a telephone equipment t, c; 
batteries b, b', and a "multiple " break wheel mw. In the 
stable, the outfit comprises a double contact key k'; a 
call box cb'; an indicator i, with gong g; telephone outfit 
t',c', and battery b." The keys k and k' are so arranged that when either of them is 
depressed it actuates both call bells, but does not operate the indicator i, in the stable, 
which instrument is only operated from the central office by the multiple break-wheel 
Mw. On the top, d, of the case of the multiple break-wheel, numbers,correspondino- to 
those of the signal boxes, are marked, as shown in Fig. 353. 

When a call for a wagon or ambulance is received tlie attendant at the central 
office places the pointer p, Fig. 352, at the number corresponding to that from whicli 
the " call " has proceeded, and then pulls upon the crank lever l, whereupon taat 
number is automatically transmitted over the indicator circuit to the stable and is 



4/6 



AMERICAN TELEGRAPHY. 



Struck by the gong and recorded visually by the " indicator." The manner of opera- 
tion of the indicator is described in connection with the Gamewell fire alarm telegraph. 
AUTOMA'iic TRANSMITTER, OR MULTIPLE BREAK-WHEEL. — The general principle of 
the multiple break-wheel or transmitter, will be readily understood by reference to 
Fig. 354j ill whinh p is the pointer and l the crank lever seen in Fig. 352. wis the mul- 
tiple break-wheel, mounted on a shaft ./'. This shaft extends above the cover d of the 
box in wliich the wheel is encased, and the pointer is rigidly attached to it. Conse- 

FIG. 352. 




GAMEWELL CENTRAL OFFICE.— STABLE ELECTRICAL CONNECTIONS. 

quently, as the pointer is moved around, the break- wheel is turned with it. The break- 
wheel consists of concave strips of metal, on the outer edge of which, teeth correspond- 
ing in number and arrangement to the numbers of the signal boxes, are projected, as 
indicated in the figure. s,s' are contact strips, supported as shown, by a shaft a. 
Normally, these strips are separated. The effect of pulling the crank lever to the 
left is to give the shaft a a half turn, or more, which act gives the contact strips «i 
downward sweep, indicated by the dotted line. In making the downward sw^eep the 
small lever / on the end of s' comes into contact with the teeth that may be in its path 
and rides over them, without moving the strip s'. When the crank lever l is released 
a recoil spring, not shown in the figure, returns the shaft a to its normal position. In 
its return sweep the small lever /on the end of s' again engages with the teeth, but, 
as now it cannot yield, it forces the strip s' down upon s thereby closing the " indica- 



THE GAMEWELL POLICE SIGNAL SYSTEM. 



477 



tor" cireiut. This act is repeated at each tooth with the result that the box number 
is transmitted. In the iUustration the box number transmitted would be 23. 
In the transmitter box as act- „,„. ^^, 

FIG 353. 

ually used, an arrangement is pro- 
vided whereby the circuit is kept 
open at another point during the 
downward sweep of the contact 
strips, lest by any means the con- 
tacts should be thrown together 
at that time; but immediately on 
the commencement of the upward 
sweep the extra opening is closed. 
Means are also provided whereby, 
when the crank lever has been 
pulled, the pointer p is locked until 
the box number has been trans- 
mitted. These devices have been 
omitted in the figure for the sake of clearness. 

As the element of " time " enters largely into the successful operation of the " in- 
dicator " care is, of course, taken that the teeth representing figures shall be separated 
by equal distances in every case. 




FIG. 354. 




MULTIPLE TRANSMITTER OR BREAK WHEEL. 



Gamewell police telegraph boxes. — The Gamewell police telegrapli box is 
shown in its three positions in Figs. 355, 356 and 357 : namely, with both doors closed, 
with the outer door open, and with both doors open. 



478 



AMERICAN TELEGRAPHY. 



In the practical operation 



FIG. 355. 




when the outer door is closed ; 
grounding of the circuit 
operates the central office 
bell as described. 

Normal h^, the gong mag- 
net G, within the box, is 
cut out of the circuit when 
the outer door is closed^ 
by the pressure of that 
door upon a knob n, Figs. 
356, 35 7- When, how- 
ever, the " citizen's " key 
is inserted in its key- hole 
the gong magnet is placed 
in the main circuit and 
becomes operative. 



Ordinarily, the police 
officer in pursuing his 
rounds, opens the outside 
door and places the 
pointer at '•' re])ort,"' after 



of this system a signal can be transmitted by insert, 
ing and turning a key in a key-hole provided for 
the citizen's key. The turning of this key has 
a similar effect to pulling down the crank lever 
by its handle. When the key has been inserted 
in the " citizen's " key-hole and turned, it cannot 
be withdrawn until the outer door^has beeu 
opened, but, immediately upon its release, a spec 
ial wagon signal is transmitted to headquarters 
and the nature of the special signal,which appears 
on the paper strijj as a long dash preceding the 
box number, indicates to the attendant that the 
"call " has been transmitted by a '"citizen's" key. 
This is accomplished by a device within the 
on the inside of the inside door, Fig- 
and, at the same time, 
a shoit time, 
just prior to the sending in of the box number by 
the break-wheel bw. At the same time, also, the 
special wheel svv is cut out of the circuit, so that 
it is immaterial at what point of the dial tlie 
pointer p, Fig. 356, may be inadvertently left 

the citizen's signal only will be transmitted". The 
FIG. 356. 



case, c, 

357, which opens, 

'^ grounds," the main circuit for 




which he pulls the crank, which, by transmitting 
the signal, announces to headquarters his presence at a certain box. An "answer 



THE CHICAGO POLICE PATROL TELEGRAPH SYSTEM. 



479 



back " signal on the bell, within the box, informs him that his report has been received 
and he may proceed on his " beat." If the policeman should be wantec^ for any reason 
by tlie central office, a pre-arranged number of strokes on the bell notifies him to use 
the telephone. Should the central office attendant require to leave his desk he may 



FIG. 357. 




set a device which will automatically transmit this pre-arranged signal immediately 
after the completion of the officer's signal, thereby holding him. One means by 
which this is accomplished is shown in connection with the .viunicipal patrol system. 
The arrangement of the telephone apparatus is shown ^clearly in Figs. 356 and 357. 
The "transmitter" battery is held in a receptacle b under the roof of the box. The 
condenser, which is used to complete the telephone circuit, as outlined in Figs. 350, 
352, is shown as c' in Fig. 357. 



The Chicago Police Patrol Telegraph System. 

In the operation of this system it is the practice to have an attendant constantly 
at the " cabinet," (as the desk in, or on, which the central office apparatus is placed, is 
called) in Police headquarters. It is the duty of the attendant to note and acknowl- 
edge receipt of every signal. Consequently, it is not considered necessary to employ 
*' alarm " apparatus in the signal box when a special signal is to be sent ; nor apparatus 
in the central office to respond to the same. With this exception tlie signal box and 
central office apparatus of this system is virtually similar to that of the '' Gamewell '' 
already described; tlierefore, only such features of the Chicago system as differ from 
those of the Gamewell system need be here described. 



48o 



AMERICAN TELEGRAPHY. 



The eleci.rical connections of the Chicago police patrol telegraph are outlined in 
Fig- 35 S- SB is the patrol, or signal box apparatus, bw is the "number" break- wheel, 
sw the "special" signal wheel, cb is an "answer back" bell. t',c' tlie telephone apparatus. 
3K is an ordinary strap-key, on which code signals may be tapped out by an officer. 

The apparatus at the central office, CO, is shown at the right of the figure. It 
consists of the relay r, register kg, a '' push jack " h, magnetic coil mc, line galvano- 
meter G, main battery b, local batteries b and b\ lightning ai-rester la and tele]»hone 
outfit T,c. A stable outfit, similar to that employed in the Gamewell police telegraph 
system, but not shown in Fig. 358, is employed. 

FIG. 35S. 



U^^tvW, 




CHICAGO POLICE PATROL CIRCUITS — THEORY, 

; "\Mien a signal is received, it is, as stated, acknowledged by th' attendant in the 
central office, either by the telephone, or by means of the push-jack. The function of 
the push-jack, when depressed by the hand and withdrawn by a spring, is, first, to 
charge the coil mc by the battery b^ and, next, to j^ermit its discharge through the 
main circuit. It will be noticed that the metal strips m,m' on h, when the latter is 
pushed down, form a circuit for battery b through mc, and that, on the withdrawal of 
the push- jack, the connection with the battery is broken at x' before the longer strips 
s,s' sever connection with the strips m,m' on the push-jack. This gives the magnetic 
coil an opportunity to discharge through the main circuit, thereby momentarily in- 
creasing the current on that circuit, and operating the " answer back*' bell in the sig- 
nal box from which the signal had emanated. 

The manner in which the •' answer back " bell is operated is as follows: Refening 
to Fig. 358, it will be seen that that bell, cb in SB, is cut out of tho main circuit by the 
short-circuit via contact c. The bent lever l, pivoted at x^ at its upper end keeps the 
contact c closed, while, at its lower end, it holds down the armature lever of cb, VN'hich 
otherwise would be drawn up by the strong pull of its retractile spring; and this would 
occur even when the contacts at c are separated and the main line current is thereby 
permitted to flow in the coils of cb. 



THE CHICAGO POLICE TELEGRAPH SYSTEM. 



48 



FIG. 359. 



When the crank lever k of the signal box, shown also in Fig. 359, is pulled, its 
left end engages with the rod r, lifting the lever l so that the contacts at c separate, 
putting CB into the main circuit and releasing its armature lever, which is then with- 
drawn by its retractile spring. As soon as the crank lever k returns to its normal po- 
sition, the rod r falls, but is prevented from resuming its former place by the armature 
lever cb. Thus the bell cb still remains in the main circuit. The attendant at the 
central office CO now operates the push-jack and the extra current generated thereby 
attracts the armature of cb, striking the bell once and permitting the lower end of the 
lever l to move over the arma- 
ture lever again, locking it as 
before, and also closing the 
contacts at c. The stroke 
on the bell is termed the 
" answer back" signal, which 
indicates to the policeman at 
the box that his signal has 
oeen received and that he 
may now use the telephone. 

The object in using this 
" push- jack " and magnetic 
coil, it will be understood, is 
to avoid the necessity for a 
large extra battery to fu)-nish 
an extra current to close the 
bell magnet; since it is not 
desired to open the circuit for 
any other purpose than the 
transmission of *'on duty" or 
special signals. It will be 
understood also that the di- 
rection of the extra current thus set up by the magnetic coil is arranged to coincide with 
the current from the main battery; otherwise the *' counter '^ current would be apt to 
momentarily release tlie relay K when the push-jack is operated. 

The signal box SB is shown as it appears in actual service, with the door open, in 
Fig. 359, in which i is the telephone receiver Tr the transmitter; c the condenser; or. 
the " answer back" bell; sw the special signal wheel; bw the box " number " break- 
wheel; K the crank lever and P the pointer. 

The battery, of one dry cell, for the operation of the telephone from the signal 
box, is contained in a receptacle under the roof of the box. The actual connections of 
the telephone apparatus, with the condenser omitted, are shown in the Pearce and Jones 
system, next described. 

The signal box with inside door closed is illustrated in Fig. 360. The pulling of 
the lever k, shown on the outside of the door v>, by reason of the engagement of a pro- 
jection p' within the door, (sliown in Fig. 359) with a projection k on the crank lever, 
pulls down the latter in tlie usual way to operate the signaling niochanisni. 




CHICAGO POLICE PATROL BOX. 



482 



AMERICAN TELEGRAPHY. 



Special signals are transmitted by the police officer, or others having access to the 
boxes, by moving the pointer p. Fig. 359, to the designated point on the dial; which 



FIG. 360. 








n 



CHICAGO POLICE PATROL BOX. 



sismals are recorded on the register in the central office. 



The Pearce and Jones Police Patrol Telegraph System. 

This system is in successful use in several of the large cities of the United States. 
It is quite simple in its operation. 

In this system means are provided in the street signal box whereby the policeman 
on liis beat may send in the box number to indicate his whereabouts to headquarters, 
or whereby he may hold telephonic or telegraphic communication with that office, or 
send in special calls for assistance; for ambulance wagons, etc. 

Apparatus is provided at the central office for receiving, automatically, on a regis • 
ter, the number of the box, the nature of the call, etc., and also the means for holding 
telephonic and telegraphic communication with a policeman at any of the signal 
boxes. 

In Fig. 361 is shown in general outline the apparatus and connections of a central 
office of this system. The connections for two patrol circuits are shown in the figure. 



PEARCE AND JONES POLICE TELEGRAPH. 



483. 



It will be understood that as many more circuits as may be necessary can readily be 
added. In the figure dr is a double-pen register, one magnet of which is included in 
the local circuit at relay k^ ; the other in that of r^. The register is self-starting and 

FIG. 361. 




PEARCE AND JONES POLICE PATROL SYSTEM. — CONNECTIONS. 

self-Stopping. Ordinarily the telephone t is not in any circuit. Its terminals are con- 
nected with a " wedge " p, by means of which it may readily be introduced into either 
circuit, at the spring-jacks, in the well known way. This telephone is inserted in a cir- 
cuit by the operator at headquarters whenever a signal is received from a street sio-nal 
box. Relays k^ k^, having a resistance of about 80 ohms each, are alwavs in the re- 
spective circuits. These, by means of their armatures and local batteries, operate the 
registers dr. These relays are furnished witli back and front contact points, and, by 
means of the switch s, the regist(;r may be operated on either front or back contact. 



484 



AMERICAN TELEGRAPHY. 



This arrangement is valuable when the alarm circuit is broken by accident at any 
point, for, at such times, the local circuit may be switched from the back to the front 
contact, and, as soon as tlie line is repaired, the ^rmature Avill be attracted and the reo-- 
ister operated, thus automatically announcing that the repair has been made; when the 
local circuit is again switched over to the back stop. The " signal keys " are normally 

closed. They are actuated 
FIG. 362. when it is desired to operate 

the bell in the signal box, as 
will be explained. In each cir- 
cuit is placed a galvanometer 
G^ G-. The normal current 
strength of ihe circuit deflects 
the needle of this instrument 
to a certain angle. When 
the deflection is out of the 
normal it indicates either an 
open circuit, a ground, or an 
escape. The galvanometer 
EG, by means of the three- 
point switch s', may be cut in 
on either No. i or No. 2 cir- 
cuit. One terminal of eg is per- 
manently connected to ground 
so that, when a circuit is con- 
nected to its other terminal, 
the presence of an escape or 
ground on the circuit will be 
indicated. The "stable call" 
is used in announcing to the 
ambulance people that their 
services are required. 

The connections and appar- 
atus of a street signal box are 
shown in Fig. 362. It is 
about the size of the usual 
street fire alarm box, and is 
similarly provided with 
tight doors, etc. In this figure bw is a break-wheel of peculiar construction, by means 
of which regular and special signals are transmitted, k is a strap, or signal key by 
which, as in the manner of the ordinary Morse keys, signals may be "tapped" out. 
As, however, expert operators are not available, this key is only used for the purpose of 
sending in code signals, according to a printed blank attached to the inside of the door 
of the box. The bell b is operated by the central station when such code signals are 
being transmitted to the policeman at the box. A telephone receiver tr is contained 
within the box, also a telephone transmitter t, and the usual induction coil, zV, and the 




PEARCE AND JONES SIGNAL BOX, 



PEARCE AND JONES POLICE TELEGRAPH. 485 

transmitter battery tb. Usually the telephone receiver is suspended from a hook h, at 
which time the telephone battery is out of the circuit, being open at .r, and the 
bell, B, is then in the circuit, but, when the telephone receiver is in use, the hook is 
pushed up against x and the telephone battery is put into the circuit by way of contact 
:x, while the bell b is cut out of circuit at the contact f, as will be easily understood by 
examination of the connections. The " cut out '' n at the top of the box is operated by 
an attachment on the outer door of the box, which forces the contacts c' together, thus 
cutting out the apparatus within the box, as is customary in the case of many fire alarm 
signal boxes, and for the same purpose, namely, to diminish the resistance of the cir- 
cuit by short-circuiting the induction coils, magnet coils, etc. 

The break-wheel bw, within the large box, is enclosed in a metallic case c, from 
which the cover is, in the figure, removed. The apparatus, bw, consists of a brass wheel, 
on the periphery of which are projections i, 2, r, r, etc. This break- wheel, mounted 
on a shaft a, to which is attached a recoil spring, is revolved in the usual manner. The 
main line circuit i, i, is led, by insulated wire, to two flat contact strips s, s'; the up- 
per of which extends somewhat beyond the lower at a. A small lever /j^ivoted at ^ 
is held in the jiosition shown by a light spring s^. When the wheel bw is turned, by 
the crank handle, in the direction of the arrow, the lever / simply slides over the pro- 
jections without separating the contacts s, s', which are normally together. But, when, 
in obedience to the recoil spring, the wheel bw reverses its motion the lever / cannot 
yield, but, instead, rides over the projections r', r', etc., and, consequently, the upper 
contact s is forced to rise, breaking the circuit at r. The number of such breaks will 
depend on the number of projections over which the lever may be caused to ride. In 
practice, in this system, the projections representing the number of the signal box are 
set nearly together, as 1,2 and 1,2,3. Further along the periphery, similar projec- 
tions r', r', r' are placed, at greater intervals. These latter are the means by which 
emergency calls are given. For instance, if the wheel bw is turned so that the lever b 
passes the projections 1,2 and 1,2,3, ^"d is then stopped, only the number of the box, 
assuming it to be, in this case, 32, will be sent in, but, if the wheel is turned until, for 
example, the projection marked "fire," on the dial. Fig. 363, is reached, the sig- 
nal sent in would be 3 slow strokes, and then the number, 32, as before. This would 
indicate to the central oftice that a " fire " signal had been sent in from box 32. Had 
but 2 slow strokes and the " number " been received, it would have indicated that an 
ambulance was desired at the box 32. 

In practice there is placed on the outside of the cover of the case, shown in Fig. 
363, in which the break-wheel is enclosed, a depressible projection p, which, normally, 
stops the downward motion of the crank lever k at a point at which it will have turned 
the break-wheel to a position where only the ordinary number of the box will be sent 
in. Thus it is only necessary in ordinary circumstances to pull the crank lever as far 
as it is free to move. When, however, an emergency call is to be made, a knob, n, 
which also extends outside of the cover of the case c, is pressed in. This action re- 
moves the obstruction p out of the path of the crank lever and allows it to be pulled to 
any desired point on the dial, whereuj)on the crank is let go and is returned to its start- 
ing point by the recoil spring; the break- wheel, at the same time, sending in the de- 
sired siirnal. 



.86 



AMERICAN TELEGRAPHY. 



FIG. 363. 



Inasmuch as one of the objects of a police patrol telegraph system is to provide a 
means whereby the policeman may announce his exact whereabouts, thus showing that 
he is faithfully patrolling his *' beat," it is evident that means should be devised to 
prevent him from outwitting the box, which he might do l^y tapping off the number of 
a box located at some other point than that at which he has arrived. In otlier words, 
to prevent him, for example, from remaining at any one box and from that box send- 
ing in signals corresponding to the various boxes at which he should have arrived, at 
given times. This he might do, if not thwarted, by imitating by means of the sig- 
nal key K in the street box, the action 
of the break- wheel in sending in the box 
number. 

To avoid this possibility, in the 
*' Pearce and Jones " " patrol " box, tlie 
signal key k is normally cut out by means 
of the contact points r/. Fig. 362, con- 
tained within the break- wheel case c. 
These contacts are only se})arable by 
turning the break- wheel until the insu- 
lated piece / attached to the shaft a, 
reaches the contact strip at /', when the 
contacts are separated. / is so placed 
that it does not break the contact at c/f 
until the wheel bw has reached a point 
where, on its being released, it will auto- 
matically send in the number of the 
box. Consequently, when the officer 
desires to communicate by means of th3 signal key k, he must first turn the crank 
of BW to its ordinary extent, and then hold it there until he taps in his code signal. 
It would, of course, then be useless to send in a false box number, by means of the 
signal key k, inasmuch as it would be immediately followed by the correct number, 
upon the release of the crank lever. 

The lightning arrester la, shown in Fig. ^62, is of the usual form. 
In the cities where this system is in operation the officer on reaching a patrol box 
is required to use his telephone to converse with the attendant at headquarters to re- 
ceive instructions, etc. In case the telephone is not in working order the emergency 
call is used, or the emergency call may be used in addition to the telephone message. 

No means are employed on tliis system to prevent the passage of box number sig- 
nals over the circuit from interfering with the use of the telephone ; the interruption, 
if any, being only of momentary duration. Should two officers open different boxes 
simultaneously, they hear each others conversation and one refrains until the other has 
completed his conversation with the central office. 




Where it is desired to announce a special call by an extra alarm in the cen- 
tral office, additional devices may be added to those shown at CO in Fig. 361. One 
such device, due to Mr. J. W. Stover, is outlined in Fig. 364. 

In this figure CO represents the central office in which g is the recording register 



STOVER SPECIAL ALARM. 



487 



and R is the main line velay, which, by its armature lever, operates g. mb is the 
main battery. B ij* a 'street patrol box. The apparatus employed to give the special 
alarm in the central rffice consists of a magnet rm in tlie patrol circuit, and a vibrating 
bell CB, whose local circuit is controlled by the armature lever of rm. The armature 
of RM is so adju^^t'^d that the usual current on the main circuit will not attract it. 
At such times it retains in a vertical position, by means of its hook end e, the up- 
right rod L. When, however, by any means, the current on the line is increased, the 
armature of 2m is attracted, upon which its lever releases the rod l which falls 
QV^r on th3 contact point p, thereby closing the local circuit of cb, vibrating its bell. 

FIG. 364, 





.. CO. 

ii— V .- • 

I I - 

£\ _4 ^ »>ip^ 



llllllll 

MB 



Rh. 



A 



s\ 




STOVER SPECIAL ALARM DEVICE. 



To produce this increase of current on the line, special arrangements are pro 
vided in the signal box 13 and in the central office. In the signal box a spring 
connected with the " ground," is so placed that, when the crank lever is turned be 
yond the ordinary stopping point, it momentarily grounds the main circuit. A 
"ground ■' is permanently put on the main line in the central office by either the 
switch s or s'. s is used when the rheostat Rh of moderately high resistance is em- 
ployed. The effect of grounding the circuit at the signal box is to '* short-circuit'' 
the rheostat. When the switch s' alone is employed andRh is dispensed with, the 
act of "grounding'' the main circuit in the signal box short-circuits the relay 
K, Either operation increases the current flowing in the relay rm and actuates it, 
thereby calling the attention of the attendants in the central oflice to the fact that 
a special signal is to be sent in. The lever l of rm requires re-setting manual Ij/, 



488 



AMERICAN TELEGRAPHY. 



after each special signaL One side of the crank lever of B is insulated, as shown, 
so that the line wire is not grounded on the return trip of the crank. 



FIG. 365. 



The Municipal Police Signal Telegraph. 

This police patrol system varies somewhat in its arrangement from those already 
described. 

The apparatus employed consists of the usual street signal box for the trans- 
mission of signals, and, in the central office, relays, registers, time stamp,etc. 

The signal box is shown with both doors 
closed in Fig. 365. In Fig. 366 it is shown 
with the outside door open. It will be noticed 
that the pointer is arranged somewhat differently 
from those shown in the systems previously 
described; being placed, when at rest, at the 
center of the dial. The handle of the pointer 
is made in such a way that the act of shutting 
the outside door insures that a knob k shall 
place the pointer in its normal position. 

Signals may be sent in by the act of turning 
a key in the key-hole, shown at the bottom of 
the door. Fig. 365, or, by pulling clown the hook, 
shown in Fig. 366. 

The arrangement of the apparatus within a 
patrol box is shown in Fig. 367; in which 13 
is the telephone battery and c is the condenser 
used in connection with the telej^hone. The 
special signal apparatus and the box '' number " 
break-wheel are contained within the case \\\ The 
winding shaft of the break- wheel, etc., is connected 
with a long strip s,the pulling down of which, by the turning of the key, or by the 
pulling of the hook referred to, operates the signaling wheels. The "answerback'' 
magnet g at the side of the case w, is a polarized magnet which is only responsive to 
reversals in the direction of the current on the main line, which reversals are caused 
by a pole-changer in the central office. 

A multiple pen register, and time stamp, employed in the central office, are shown 
in Fig. 368. The register case contains, on one side, the multiple pen apparatus, 
and, on the other side, apparatus used in connection with '•' answer back " signals, or 
for the automatic transmission of signals to indicate to an officer that he is desired 
to use the telephone. 

In the operation of this system "special" signals are indicated by an "alarm," 
or annunciator " drop," in the central office. 

In Fig. 369 is shown a theoretical diagram of circuits and apparatus in a central 




POLICE SIGNAL TELEGRAPHS. 



489 



office nnd signal box, by means of which the various signals mentioned may be trans- 
mitted and received. CO is a central office, in which are placed a relay R, controlling, 
bv its armature, a reg- 

T FIG. -^66. 

ister g; an ordniary 
duplex pole-changer PC, 
which, when operated, 
reverses the main bat- 
tery B in the u^ualway. 
A is an annunciator mag- 
net, or electric bell, v 
is a grooved screw, 
geared with the clock- 
work and started by the 
register lever ; this screw 
tends to bring a lever 
I into connection with 
d contact point x con- 
trolling the annunciator 
circuit. This piece of 
mechanism may be con- 
sidered as analogous in 
its operation to that 

of the self -starting and .17- iw 

Stopping apparatus of Morse register. In this ca.e the lever / is nomally 

FIG. 367. 





held out of the groove of y l>y the ai-mature lever /' of the register. When the latter 
is closed the knife edge of the lever / is placed in that groove v, whereupon it 



490 



AMERICAN TELEGRAPH!. 



quickly starts to complete the local circuit at x, and, if the register's armature lever is 
not at once raised it will do so, thereby ringing the annunciator bell. If, on the con- 
trary, the armature lever is only momentarily depressed the lever /is thrown out of 
the screw thread and the spring s draws that lever to its back stop x' . Hence a dot, 
or series of dots, sent over the police circuit, from a street box, will not 
operate the annunciator drop, but a more prolonged signal, such as a dash, will. It 
will, therefore, be plain that if ordinary signals, such as may be used to note the ar- 
rival of an officer at a box, are composed exclusively of *' dots, " the '■ alarm '' in the 
central office will not ring ; while, if a special signal is made up of one or more dashes, 
time will be afforded to close the alarm circuit. 

It will be seen presently how these long and short signals are automatically 
transmitted, as desired, from the signal box. 

FIG. 36S. 




As has been intimated, means are provided in the central office for calling up an 
officer on his arrival at the patrol box in the absence of the attendant at the central 
office. This consists of an arrangement of the gearing in the register box, whereby a 
wheel M, at the recurrence of each signal, is caused to make a revolution. On its 
periphery are three teeth over which a contact Gpring/r rides, thereby making con- 
tacts with the contact cs and closing the local circuit of the pole-changer PC at those 
points. Nor'nally, however, this local circuit is open at a switch s, so that the fact 
of the closing of the circuit at fs, cs, on receipt of every signal coming in on the 
circuit does not affect the pole changer. But, if, as when an officer is desired to use 
his telephone at the signal box, the attendant in the central office closes the switch s, 
the effect of closing the local circuit of pc at/Jr, cs, will be to operate the pole-changer 
a stated number of times, corresponding to the teeth on the periphery of m. These 
teeth are placed at a point on the periphery where they will not affect the contact 
strip /$■ until almost at the end of the revolution of m. Thus, when the switch s is 
closed the act of the officer in reporting his presence at a box will eventually cause 
tlie pole-changer to reverse the direction of current thrice on the line, which reversals, 
by ringing the bell in the signal box an equal number of times, will signify to the po- 
liceman that he is required to communicate with the central office. 



POLICE SIGNAL TELEGRAPHS. 



491 



The theory of operation of the pole-clianger and polarized relay will be found 
described in the chapter on the polar duplex. 

In Fig. 369 also, SB is the street signal box, in which are shown only a multiple 
break- wheel bw; a pointer f; a cylinder c, with spirally arranged projections/; 
the '' answer back " bell, g; the telephone t, and condenser c'. 

The multiple break-wheel shown consists of a shaft on which a number of break- 
wheels,z£/^, w-^ w^^ w"^, are placed, as indicated. Over these wheels flat contact strips 



FIG. 369. 




POLICE PATROL SIGNAL CIRCUIT.- 



-SHOWING AN ARRANGEMENT FOR 
OFFICE. 



ANSWER BACK " SIGNAL IN CENTRAL 



/^,/2,/^,/*, are held, by a common support h. Above these flat contacts the cylinder c 
is placed. The pointer p is attached rigidly to the shaft of c. Thus, wiien the 
pointer is turned to the right or left the cylinder c is moved a corresponding distance 
to the right or left. When thus turned the effect is to cause one or other of the pins 
/ to depress and push a flat contact strip into contact with the periphery of its respec- 
tive break-wheel. The box " number " break-wheel, nb, is shown on the end of the 
multiple break-wheel. It has a separate contact strip f. The main line circuit is 
connected to the break- wheel cylinder; and to the strips p and h, as shown. 

The break- wheels/^, /2, etc., are, in the figure, arranged to transmit "wagon," 
"telephone" and " report " signals. For example, the telephone signal may be rep- 
resented by a tfo/, dash, dof^ followed by the number of the box, thus: ; 

the wagon signal by two dashes, followed by the box number, thus: , 

etc., assuming the box number,in each case, to be 24. Hence the '' telephone" break- 
wheel ze/g ^ill b^ equipped with three breaks, corresponding to dot, dash, aof^ and ti:^ 



492 



AMERICAN TELECxRAPHY. 



" wagon '' signal wheel Wo^ , with two breaks, corresponding to two dashes. Other 
break-wheels may be arranged, as desired. 

Owing to the spiral arrangement of the pins on cylinder c only one special sig- j 
nal strip will be depressed at one time by the turning of the cylinder. 



FIG. 370. 



FIG. 372. 





It may be seen that the long break in the periphery of the number break- wheel 
NE is placed at a point where the continuity of the circuit is taken up by one or other of 
the flat springs /1/2, etc., by contact with a break-wheel; and that a similar long break 
is made in the periphery of the other break- wheels at a point where the continuity 
of circuit is taken up by the box number wheel. 

When an ordinary signal, such as a " report for orders," which might be rep- 
resented by one dot preceding the box number, is transmitted, the special alarm in 
the central oflfice is not operated, for the reason that the break has not been of suffi- 



POLICE PATROL BOXES, 



493 



cient duration to permit tlie closing of the " annunciator " circuit. When, however, 
a " Avao'on " or " telephone " signal is transmitted, the spaces on tlie break- wheels as- 
signed to those signals allows the lever / at CO to be moved over to x, thereby closing 
the annunciator circuit, with the result stated. In Fig. 368 the break- wheel at SB is 
represented as just having transmitted an ordinary box number signal, as indicated at CO. 

There is, in addition to the apparatus shown in Fig. 368, at SB a device whereby, 
when a signal is transmitted by a citizen's key, from the key-hole on the outside door, 
a dash twice the ordinary length is recorded on the register. This not only gives the 
" alarm" of a special signal, but also indicates that the special signal has been actuat- 
ed by a citizen's key. ' 

Galvanometers for testing circuits, multiple break-wheels for tiansmitting tlie 
calls for wagon to the stable, and rotating switches for connecting up any circuit 
with the telephone, etc., practically similar to those already described in connection 
with other patrol systems are also used in the central office of the system just de- 
scribed. 



of tlie various companies 

FIG. 371. 

I- 



are 



POLICE PATKOL BOXES. 

As previously stated the signal or patrol boxes 
placed on walls, in booths or on 
lamp posts and telegraph poles, as 
may be most convenient. 

In Fig. 370 is shown a lamp post 
box. This box is provided with 
signaling apparatus virtually as 
described in connection with patrol 
boxes j but has, in addition, an 
attachment known as the Tooker 
"keyless door.'- This door may be 
opened without a key, by any citi- 
zen, by turning the handle until 
the door opens, but, as the handle 
is turned, a loud gong is struck 
repeatedly, giving notice to ad- 
jacent policemen, or others, that 
the box is being opened. 

The same box with the outside 
door opened is shown in Fig. 371; 
the gong being contained within 
the round case c. The door may 
be opened from the outside by a policeman with a key Avitliout ringing the oono-. 

A booth and box are shown in Fig. 372. The door of the booth is iiormallv closed. 




* 



CHAPTER XXX. 



KAILWAY ELECTRIC BLOCK SIGNALING SYSTEMS, ETC. 

A " block '' system, in brief, consists of a plan for the showing of sis^nals, manually, 
or automatically, which indicate to the engineer of an approaching train that a certain 
section of the track in advance of him is " clear " or '' occupied." That is, either that 
there is or is not another train on the section before him. These " sections " or "blocks" 
are divided into various lengths, depending in a great measure on the topography of 
the road or the amount of traffic over it. In some cases the sections do not exceed 
i,ooo feet; in others they may be several miles in length. 

Electricity performs a very important part in many of the " block " systems now 
in operation on railroads of this country. 

Block system.s are of at least two kinds. Namely the " absolute block " and the 
*' permissive." In the absolute, but one train is allowed at one time on any one 
block; and the signals displayed at the entrance to such a block is either " safety " or 
^* danger." In the permissive system, a second, or even a third, train is allowed on 
the one block, under certain conditions. The signals employed on the block systems 
are either " safety, " " caution," or danger." 

The " safety " signal consists of a white sign or white light. Tlie "danger" sig- 
*iial of a red sign or red light. The " caution " signal of a green sign or green light. 

In automatic electric block systems the circuits and mechanism are generally so 
arranged that the entrance of a train into a " block " sets the " danger '' siscnal, and 
that signal is continued until the train passes out of that block into the next, when 
the danger signal is lowered and the safety or caution signal, shown.* 

The part assigned to electricity in the operation of these signals, when that 
agent is employed, consists, as a rule, in actuating electro-magnets which are placed 
in circuits capable of being opened, closed, or short-circuited, by the engine or cars 
of a train. These electro-niagnets in turn are caused, either directly or indirectly, to 
operate the various signals. 

Tlie laws, or facts, of electricity and magnetism involved in effecting the forego- 
ing results have been fully stated elsewhere herein, but, for conrenience of explanation 
may be repeated here. They are, briefly, as follows: A rod or bar of soft iron sur- 
rounded by an insulated coil of wire becomes a magnet when a current of electricity 
is caused to flow in the coil. The current of electricity may be set up by any suit- 
able source of electromotive force. As long as the current circulates in the coil the 
bar remains a magnet; when the current ceases, the iron ceases to be a magnet. 
While the iron continues a magnet it will attract its armature ; when it ceases to be 
a magnet the armature is released. The current through the magnet coil may be dis- 
continued by opening the circuit at any point; or it may be diverted from the coil 

* In some block signal systems, what is termed the '^ normal danger" plan has been somewhat recently adopted, 
Avhereby the " danger""' signal is normally shown until the approach of a train, when, if the immediately preceding sections 
{ire clear, the signals go to '• safety.'' This plan is intended to lessen, among other things, the likelihood of signals stand- 
ing abnormally at •■ safety," due to mechanical defects, or other causes, such as sleet storms. 



THE UNION SWITCH AND SIGNAL. 



495 



by providing a sliorter circuit for the current than that offered by the coil. Botli 
of these methods of demagnetizing electro-magnets are availed of in railway electric 
signaling. 

In some electrical systems of block signaling, for instance, the Union Electric 
Switch and Signal system, the rails of the tracks are used as part of the electric cir- 
cuit, in the manner to be described. In other systems, as, for example. Hall s rail- 
way signal system, the wheels of the train operate a mechanical " circuit maker " or 
"breaker" which causes the desired movements of the sisrnals. 



The Union Switch and Signal Electro-Pneumatic Block System. 

In the block system of the Union Switch and Signal Company, one of the methods 
of signaling employed is a combination electric and pneumatic system. 

In Fig. 373 are sliown, theoretically, fig. 372 «. 

the electrical circuits and connections 
of this system as arranged for one 
track of a double track road. In the 
figure the position of the armatures of ^p/ 
the relays and magnets, and the 
position of the semaphores, in four 
different blocks, are shown as tiiey 
would appear in practice under the 
conditions described further on. 

Compressed air is employed to effect 
the doAvnward movement of the 
semaphores against the weight of a 
counter poise. Tlie compressed air is 
conducted from compressors placed at 
suital)le points along the road, by a 
large pipe, indicated as p. Fig. 373, to 
reservoirs r, as shown at A, from 
which it is conducted by smaller 
pipes to air chambers on the posts 
supporting the semaphores. T h e 
electrical portion of the system is 
utilized to open valves which admit 
the compressed air into the air cham- 
bers. 

The semaphores, of which there are 
two at the entrance of each block, are 
placed one below the other on the 
supporting post. The upper semnpliore is square at its end and is painted red. The 
lower semaphore is iish-tail sliaped and is painted green. Hie upper one is termed 




tlie " home" scmapliore; the lower one, 



semaphore. 



496 AMERICAN TELEGRAPHY. 

When both semaphores are set at right anales to the supporting post, as atC? 
in the figure, it is an intimation that a train is on the " block " guarded by those 
semaphores, and when thus set they are said to be in the " danger" position. 

When the " home " semaphore is down, or at "safety," while the "distant" 
semaphore is up, or at " danger," as at B, it is an intimation that a train is one block 
in advance of that post, and when thus set the signal is one of " caution." 

When both the " home " and the " distant " semaphores are down, as at A and 
D, they are said to be at "safety," and in this position it is an indication to the en- 
gineer that, for at least two "' blocks " in advance, the track is unobstructed. 

The arrangement of the apparatus of this system is such that whenever any part 
of the electrical connections becomes impaired the semaphores are automatically 
"set " in the danger position. As the description proceeds the manner in which this 
result is accomplished will a^^pear. 

Each semaphore {see also Fig. 372^) is pivoted at x on its supporting post and it 
is furnished with a counterpoise cp, which, when not prevented from so doing, tilts 
the semaphore at right angles to the post. 

Each semaphore is equipped, on its short end, that is its left end in the figure, 
with a circular glass pane, kp. In the case of the upper semaphore the color of the 
glass is red, for danger; that of the lower, or distant semaphore, is green, for caution. 
At night, lamps are placed in such positions on the post that, when both semaphores 
are at "safety," two white lights are shown, one above the other. When both sema- 
phores are at danger, a red light is shown above a green light. When the upper, 
or home, semaphore is at safety, and the lower, or distant, semaphore is at right angles 
to the post, a green light is shown below a white light, signifying *' caution." These 
results, it will be readily understood, are due to the simple fact that, when the sema- 
phores are at right angles to the post, the colored glasses kp on the ends of the re- 
spective semaphores are interposed between the lamps and the observer. 

A view of one semaphore, with a portion of the air chamber cut away for pur- 
pose of illustration, is shown in Fig. 372^. The air chamber ac in which the 
piston head h with its rod r, works, is placed on the post below the sema- 
phore which it operates. A branch pipe bp, leading from the reservoir (r Fig. 
373) is led into the air chamber, from which, however, it may be cut off by a 
valve rod vp, within the air chamber, which valve rod is held in control by the 
armature a of an electro-magnet m. The valve rod is attached as shown, to the ar- 
mature a. On the lower part of the valve rod is a small port through which, when 
the armature is attracted, air passes, from the branch pipe bp, into the chamber. This 
compressed air acts on the piston head h and depresses it. The piston rod r, being 
attached, at its lower end, to a rod connecting with the semaphore, as outlined in 
the figure, it follows that the act of depressing the piston head lowers the semaphore 
to the safety position. 

When the air pressure is removed, as it will be when the armature a is with- 
drawn by its spring s, and the " supply " port hole is again closed, the counter poise 
CP, will raise the semaphore to the danger point; the air remaining in the air cham- 
ber escaping at the " exhaust " port. 

As already stated, for a portion of the electrical circuits required in the opera- 



THE UNION SWITCH AND SIGNAL. 



497 



tion of tliis block system, the iron rails of the tracks are used. For another portion 
separate wires are employed. The rails of one block are insulated from those of the. 



F»G. 373. 




ELFCTRO-PNEUMATIC RAILWAY SIGNALS— THEORY— UNION ELECTRIC SYSTEM. 

next block by the insertion of an insulating medium between the end rails at tlie 
dividing points of the blocks, as at 1,1, in Fig. 373, in w^hich t,t are the rails. To 
insure a thorough connection between the rails of each block a piece of galvanized 
iron vvire is connected by a rivet, across the tish-plate, or junction plate, of each rail. 



4.98 AMERICAN TELEGRAPHY. 

A small battery SK of two cells, "gravit}-," is connected to the rails as shown; 
one such battery for each block. lu eacli block a relay Ei,R2,R3,R4, is inserted into 
the circuit formed by the rails. As long as the '* block" in which any relay is placed, 
is clear, as at A, B and D, current from battery sb flows through it, and holds its ar- 
mature on the ''front" stop. When the track is short-circuited, however, as by the 
wheels E of an engine or car, as shown between C and D, Fig. 373, the current is 
diverted from the relay and its armature is withdi-awn by its retractile spring. 

It may be seen that a circuit, via wire 3, from the earth at C to the earth at B, 
includes a large battery B3, the magnet Mg at C, the magnet M3 at B, and the arma- 
ture of relay K3. A branch wire WB3 leads from wire 4, via a circuit closer c.r^^ 
which latter is so placed as to be closed when the home semaphore 11S3 is at right 
angles to the post, and to be open when that semaphore is at " safety." 

A circuit similar to 3 formed partly by wire 2, passes through magnet M4 at B, 
battery B 2, the armature of R 2 magnet Mj^ at a, to ground; and a branch wire wbj^ 
leads from wire 2 at a to circuit closer cxj^. 

In the same manner a similar circuit (and branch wire) connects one block with 
the next, throughout the system. Normally, these circuits are closed, and the branch 
circuits wBj^, WBo, etc., are open, in consequence of which, magnets Mi,Mo, etc., ara 
closed, the valves in the air chambers are open, and the semaphores are forced to 11 
"safety" position. 

In the practice of this system the home signal rises first and falls first. 

In the figure, the wheels of an engine Eare assumed to be on block C to D. This, 
it is seen, has short-circuted, or diverted, the current from small battery SB3 at D, 
from magnet, or relay R3, in consequence of which its armature is withdrawn, thereby 
opening the circuit, formed by wire 3, at R3. This permits, first, the opening of mag- 
net Mq, which, in turn, closes the valve of its air chamber, whereby the com[)ressed 
air is cut off, arid the semaphore HS3 rises to the " danger" position. When it reach- 
es this point, the- circuit closer cx^ is closed, as shown, short-circuiting, lo ground, the 
branch wire'wBg at C. This, it is evident, diverts the current from battery b^ at D 
from the magnet m-, whereupon the armature of that magnet is withdrawn, cutting 
off the compressed air, thus allowing the distant semaphore DSg to rise parallel with 
HSg, also as shown. 

In this way both semaj^hores at the entrance of a given block are set at danger 
when a train is on that block. 

The train having passed out of block B and on to C, but being still in block C, 
one block in adv^jaaee*;'^ of B, we see that the caution signal is displayed at B. This 
has been accomplished by the closing of the relay Kg, due to the removal of the 
wheels from the track of block B to block C, which has closed the circuit of wire 2, 
which act, by closing the magnet m^ at B has again admitted compressed air into tlie 
air chamber at M4, thereby depressing semaphore HS2. The distant semaphore DSg 
at B, however, which had been raised to danger, by the short wire WE2 which had 
been closed at ex 2 by the semaphore hSo, still remains up, owing to the fact that the 
circuit 3 of magnet Mg is now open at relay Kg at C, and, consequently, the valve con- 
trolled by M3 is still closed. 



THE HALL RAILWAY SIGNAL SYSTEM. 499 

The engine e having passed out of block B into C, and being now two blocks in 
advance of A, the circuits of relays e^ and 113, and magnets m^ and M2, are all closed; 
hence the valves of air chambers ac^ and AC2 are open, and the semaphoi^es at A have 
been forced to " safety.'' 

The batteries used for this system are kept, when convenient, in any adjoining 
building, but, otherwise, in a vault beside the track 

The rails of the track, when the distance is not too great, ai-e found to possess 
sufficient insulation to work the system in all weathers; bat the heavy "escapes" 
necessitate tlie use of a low electromotive force 011 the rail circuits. This use of the 
tracks in connection with railroad block signaling was introduced by Mr. F. L. Pope. 

When this system is arranged to set the signals at '' danger " when a track switch 
is opened, the operation of the switch " short-circuits " the relay e of whichever block 
it may be in, with the result just stated. 

THE UNION SWITCH AND SIGNAL " CLOCK " SYSTEM OF BLOCK SIGNALING. — There 

is another method of electrical block signaling known as the Union Switch and Sig- 
nal Company's clock system, which may be described briefly. 

In this system a rotating disc in place of a semaphore, is used. The disc is 
given a tendency to rotate in one direction by a heavy weight suspended in the hollow 
of the supporting post. This weight actuates clock-work which, when permitted to do 
so, gives the disc a motion equal to one quarter revolution. The discs shows " white" 
on one side, and " red" on the other. 

The clock work is released by the opening of a relay as a train enters the block 
practically as in the manner already described in the case of the electro-pneumatic 
system. The act of opening the relay releases the clock-work, which turns the disc 
to "danger " until the train moves oif the section, when the closing of the relay per- 
mits the clock-work to make another ''step," which "turns" the disc around to 
^'safety." 

The mechanism employed in this service is especially arranged and constructed 
to act promptly and without jarring. 



The Hall Railway Signal System. 

In the Hall railway block signal system a semaphore is not used, but 
instead, a disc, enclosed within a case, is employed. The case is about 3 feet in 
diameter, and is supported on a suitable post. The disc consists of a light ring of 
aluminum across which a piece of fine, red silk is stretched. The apertures in the 
sides of the case are glazed to correspond in size and shai)e with the disc. .V lamp 
is placed outside of the case, at the side remot3 from the disc. At niglit the lamp is 
held directly behind the disc; during the day it is dropped below it to permit 
daylight to enter the case. The post and case is shown in connection with the Siow- 
art-Hall " train order " signal. 



500 



AMERICAN TELEGRAPHY. 



FIG. 374. 



The disc d and electro-magnet em, whicli operates it, are shown within the case 
C in Fig. 374, one side of the case being cut away for the purpos'e of illustration. In 
the figure the disc is shown as at safety ; it having been turned to that point by the 
action of the electro-magnet, which instrument and the manner of its operation will 
be more clearly understood by reference to Fig. 375. In that figure em is the electro- 
magnet, A its armature and d the 
top of the disc. The armature is 
pivoted at its center. The electro- 
magnet has curved pole-pieces p, 
p'. The armature is of peculiar 
construction, as may be seen, having 
two rounded "wings" w,w'. The 
disc is rigidly attached to one of 
the wings. A rod e, which acts 
as a partial counter poise to the 
disc is connected to the other wing. 
When the electro-magnet is not 
magnetized the disc drops by 
gravity and the danger signal is 
shown. This is the position of the 
disc in Fig. 375. When the circuit 
is completed and the electro-magnet 
is magnetized the wings of tlie arm- 
ature are attracted, up and down* 
respectively, by their ijole-pieces^ 
which causes the armature, as a whole, to be turned, with the result that the 
disc is removed from before the aperture of the case. As long as current is caused 
to flow through the coils of the magnet the disc Avill be held out of the way of the 
aperture. When the current ceases to flow, the disc, as just stated, drops by gravity. 

A diagram of the circuits of the Hall signaling system is given in Fig. 376. As 
already stated, the changes from "open" to "closed'' circuit are made in this 
system by the use of so called " track " instruments, which, upon the passage of a 
train, open the circuit at the entrance to the block, and close it at the end of the 
block. The instrument at the entrance is termed the " block " track instrument; that 
at the end of the block, the "clear " track instrument. In Fig. 376, bt is the " block " 
track instrument, CT the " clear " track instrument, em is the disc magnet, d the 
disc. R is a magnet, or relay, the oflice of which will be explained, b is the working 
battery. The connections between the "block" and the "clear" instnmient are 
made by wires w,w, strung on poles alongside the track. The relay e may be placed 
at any point along the route of the block. I^ormally, the contacts c at tlie " block " 
instrument are closed. At ct the contacts c' are normally open. At such times em 
and R are in the one circuit, part of which is completed through the armature a of r. 
Consequently, the disc d is at " safety " ; the armature of em being attracted. When 
a train enters the block, the wheel of the engine depresses one end of the "track" in- 
strument BT, which raises a piston p in such a manner against the spring contacts c as 




THE HALL RAILWAY BLOCK S' STEM. 



501 



to separate them. 




This has the effect of opening tlie prei^-^nt circuit of em and e. The 
result is, tlie disc d fall** to ''danger, '' and the arm- 
ature A of R drops, opoiiug tlie circuit at a second 
point .r. After the train has passed bt the piston 
p falls down, ])ermitting the contacts c to come 
too-ether again. But now tlie circuit passing through 
EM is still broken at x ; thus the disc remains at 
" danger. " When the engine reaches ct, which 
may be placed somewhat beyond the end of the 
block, it depresses one end of the lever l', raising 
the piston p', which, in this instance, closes the con- 
tact springs c'. This completes a circuit through 
the relay k, via wires w,w. This attracts armature 
A, thereby again completing the circuit through em 
and r; but, inasmuch as there are now two circuits 
for the current, and as the one through r, via wires 
w,w, has much less resistance than that through em, 
the latter still remains open, holding the disc at 
danger. When, however, the last car of the train 
passes over the "clear" track instrument ct, it 
resumes its former position, opening the <urcuit at 
c' again, whereupon a larger portion ot current 
traverses the magnet em, which is again magnetized, 
and attracts its armature, placing the disc at safety. 

By this arrangem.ent, if the battery fails, or if 
any of the connections wear out, or the wires break, 
the disc sets itself, automatically, at danger. Or 

FIG. 376. 



H^ 





I 





HALL RAILWAY HLOCK SYSTEM— THEORY. 

ff the wires w,W become crossed, that will, by diverting current from km, place tne 
signal at " danger " also. 



502 



AMERICAN TELEGRAPHY 



The relay r and the magnets are placed in any suitable place. 
One of the " track instruments " is shown in cross section in Fig. 377. In this, 
t is the rail, l is the lever, fulcrumed atx. p is a piston, contained within the upright 

FIG. 377. 




HALLS TRACK INSTRUMENT. 

tube. e,e' are india-rubber '* buffers " above and below the lever, placed there to 
ease the up and down motion due to the action of the wheels, and also to prevent any- 
thing short of a heavy weight from moving the lever. Normally, the end of the 

lever at the tube is down, owing to the 
greater weight of that end. The up and 
down motion of the piston p is retarded 
by the air within the tube, which acts as 
a cushion. The tube, or cylinder,is divided 
into an upper, middle and lower portion, 
wliich are connected by a small air port 
at F. Consequently, as the piston begins 
to rise, the air in the upper part jjasses 
into the lower chamber. But when the 
piston rises sufficiently to cover the hole 
H there is no further escape for the air 
out of the upper chamber and it 
therefore acts more quickly as a 
stopper of the piston. On the other 
hand, when the piston falls, the air which is driven through the/^;Y hole also acts as 
a cushion, retarding the fall. The amount of tiiis air pressure is regulated by a valve. 
The lower end of the lever l moves in a closed chamber h'. The 'opening through 
which the lever l enters the chamber is kept closed by the slide plates p'p' which move 
up and down with the lever. 

"^lie manner in which the piston tends to operate the electrical j^ortion of the 
circuit is shown in top view, Fig. 377^. 




hall's railway signal. 



503 



Here p is the top of piston; w,w are the wires of the circuit, connecting with the 
contact springs c,c'. When the piston is raised it pushes the key k over so that the 
springs, in this case, are brought together and the circuit completed. In the " block " 
track connections the strip c may be placed between the insulating block b and tlie 
contact c' so that, when the piston is raised, the contacts are separated, as in the case 
of '^ break " track instruments. The screw v controls the valve by which the air 
pressure is regulated. 

When switches occur in a " block," the levers connected with the switch are 
caused to operate a set of contacts properly enclosed, which operate the disc signal in 
a manner similar to that of the " track " instrument. 



Hall's Electric Railway Signal for Crossings. 
By the aid of two track instruments, electric circuits, and a method of " interlock- 
ing " magnets, a gong is caused to ring at railway crossings on the approach of a 
train, and is stopped automatically by the same train, after it has passed the crossing, 

FIG. 378. 




hall's railway crossino signal. 
The interlocking magnets and circuit connections for this purpose are shown in 
Fig. 378. m,m' are ordinary electro-magnets provided with armatures a, b as sliown. 
One end of armature lever b of m passes through a slot e in the armature lever of m'. 
A bar B is pivoted at the upper end of a in the manner shown. Two flat sprino-s o.d 
pass near two pins projecting from b. Near the u])per ends of these springs are two 
contact //to which latter the terminals of a local circuit are brought. At rest these 
contacts are separated, as in the figure. Contacts/ in this iigure being iifh\ when the 
armature a of m' is withdrawn a pin on b pushes flat si)ring d against f . Wlien tlie 
armature a is attracted contact is made at c/and broken at p /'. At tlie same time, 
the end of the armature b of m, which is cut away at e near the end, on the inside, 



504 - AMERICAN TELEGRAPHY. 

falls down and " locks " the armature of m' so that, even should the latter magnet be 
demagnetized, armature a cannot be retracted until the magnet m is magnetized, and 
thus, by attracting its armature, (thereby unlocking armature a^ permits it to recede. 

The interlocking magnets and " warning" bell and batteries are located at the 
crossing. The figure shows the circuit arranged for trains coming from west to east, 
(w to e) as indicated by tlie arrow. The track instrument t', whose office is to cause 
the warning bell to ring, may be located at any desired distance from the crossing. 
The track instrument t', which causes the ringing to cease, is placed at a point suffi- 
ciently far removed from the crossing to permit the longest trains to pass before the 
bell ceases. 

A wire composing the circuit which passes through m', leads, from the ground at 
T, to the contact points in the track instrument, thence to the ground at the crossing; 
or, if desired, a metallic circuit may be employed, instead of a "ground" at each end. 
Another wire leads from the track instrument t' to the magnet m, thence to "ground," 
at the crossing. TJie battery mb serves for both track instrument circuits, as only one 
is used at a time. .When the instruments are at rest this battery is open. 

The operation of the apparatus is as follows : — On the arrival of a train at the 
track instrument t, the circuit tlirough m' is completed. This magnetizes that instru- 
ment and causes it to attr ict its armature a. This action forces the flat strip c 
against the contact/, which completes the circuit of the gong magnet. This circuit is 
arranged on the well-known plan of the " call bell " or " buzzer " circuit; consequently, 
as long as the contact at c/is maintained the gong will ring ; which, since a \^ now lock- 
ed by b, will be until the train, after passing the crossing, reaches the track instrument 
t' at E, when the circuit through M will be completed by the operation of that in- 
strument. This then magnetizes M wliicli attract^; its armature ^, thereby unlocking 
armature a^ which falls back, allowing the contacts c/to separate, breaking the gong 
circuit at that point. 



OVERLAPPING SYSTEMS OF AUTOMATIC BLOCK SIGNALS. 

The term " overlapping " is applied to those systems in which the signals, op- 
erated by a train as it enters a section, are placed at a considerable distance behind 
the entrance of that section. A plan of one such overlapping system is shown in 
Fig. 379, in which four sections of one track of a double track road are shown. The 
rails are used as part of the circuit, as in the case of the electro-pneumatic system, 
previously described. 

The semaphore (or the disc signal) for each section is placed about twelve or fif- 
teen hundred feet from the entrance of the section which it is to guard. For ex- 
ample. Fig. 379, the signal for section b is set about the middle of section b, and so 011. 

Thus, assuming a train to be moving in the direction of the arrow, when it en- 
ters section b it will short-circuit the relay b^ thereby setting the signal b at danger, 
thus showing the officials of any other train that the immediately preceding section 
(b) is occupied. When the train arrives at section c and leaves the rails of section b, 
the signal ^' is set at danger, while signal ^ is restored to "safety," by any suitable 



THE SYKES SYSTEM OF BLOCK SIGNALING. 



505 



means, such as pneumatic pressure or magnetic attraction. In this way each signal is 
caused to overlap its own section. 



FIG. 379. 




OVERLAPPING BLOCK SIGNAL SYSTEM. 



The overlapping system is also applied to single track roads in a practically sim- 
ilar way to that just described; signals being placed on each side of the track to indi. 
cate from which direction trains may be approaching. 



THE SYKES SYSTEM OF BLOCK SIGNALING. 

The •' Sykes " system is of the manual-electric order, as distinguished from the 
systems previously described, which are mainly electro-mechanical in their action. 

The " Sykes " block system is in use in England and is also employed in this 
country. 

The signals used in this system are of the double semaphore pattern, which sig- 
nals are actuated by means of levers, by an operator located in an adjoining tower. 
The towers are connected by wires for telegraphic intercommunication. Normally 
all signals in this system are set at ''danger " and, when thus at danger, the levers 
are locked by the armature of a magnet, the latter being in a circuit controlled by 
the operator in the tower in advance. Consequntly, when a signal is placed at dan- 
ger it cannot be set at safety until the operator in the tower in advance presses on an 
instrument termed a " plunger " which opens the circuit in which the locking magnet 
is placed. The operator in the " forward " tower will not plunge for the "■ tower " 
behind him until all trains have passed out of his block. Similarly the operator in 
each tower has control of the block behind him. 

When an operator in one tower Las "plunged'' to allow a train to enter his 
block, that act locks the lever of the semaphore controlling the block in advance so 
that he cannot set his own signal clear for the approaching train until ho has tele- 
graphed to the tower in advance to plunge for him. 

The construction of the *' plunger " is such that when it has boon plunovd onco 
it cannot be plunged again until the lever controlling the signal has boon oomplotelv 
reversed and then restored to its normal position. Thus, for instance, when n pluno-es 
to allow A to admit a train he cannot repeat the operation until he iii*st rovovsos his 
own lever and thereby clears the signal for c's train to proceed. This, howovor, re- 



5o6 



AMERICAN TELEGRAPHY. 



FIG. 380. 



quires the consent of the " tower " in advance of b, namely c, who controls the lock to 

B in the same manner that b does to a". 

As the operator in the first tower a of this block system has not any one behind 

him to " plunge,'' thereby to necessitate the placing of his own signal at '•' danger," a 

portion of the track opposite, or near, the tower is insulated, 
and made a portion of a circuit which latter controls a relay 
and magnet in such a manner that when a train enters the 
insulated section it automatically sets a's signal at danger. 
Hence, when a wishes to place the signal at safety he must 
first ask the tower in advance to '^-plunge," that he may 
do so. 

The operators in the different towers communicate tele- 
graphically, (over the wire referred to) with each other, by 
"bell" taps, a certain number of taps signifying, "plunge," 
"OK," etc. 




FHE " STEWAET-HALL ' TRAIN OEDER SIGNAL. 

In connection with the Hall railway signal system, a 
recent device, termed a "train order" signal, has been in- 
troduced. One of its objects is to hold trains at any station 
where an order may be awaiting them. The " train or- 
der" semaphore is shown in Fig. 380. The Hall disc might 
y HH be used if desired. 

rir The train order signal posts are designed differently 

j n from the ordinary semaphore, or disc, ])osts, in order that the 

train men may be apprised of the exact reason for the 
display of the stop, or danger, signal. 

The electrical connections of this device are outlined in 
Fig. 381. The switch s annunciator a and battery b may 
be located in a station. The semaphore s' and electro-mag- 
net M, are in .the signal post case. 

Ordinarily the circuit is completed through the switch 
s, and the annunciator magnet, and thus the signal is held at 
" safety " by the action of its magnet. When, however, the 
station agent or operator has an order for an approaching 
train he moves the switch in such a way as to break the 
circuit, which action permits the counterpoise cp of the 
semaphore to raise it to danger, as shown in Fig. 380. The opening of 
the circuit also permits the annunciator drop to fall "w^hich, it will be seen, opens the 
circuit at a second place, viz. .t, and it also reveals the words " train order, " as shown 
at the right of Fig. 381. The object of this latter arrangement is to assist the station 
agent or operator in remembering that he holds a train order for a particular train 
which it does by making it necessary on his part, in order to reset the signal at safety 



TRAIN ORDER POST, 



TRAIN SIGNALS. 507 

not only to move the switch back to its normal position, but also to push back the 

FIG. 381, 






i 


^^f ■ 


1 TRAIN 1 


4 




# 








iSiiil 

ORDER 

u 





STEWART-HALL TRAIN ORDER SIGNAL. 



"train order" annunciator. In practice the annunciator boxes are marked "west 
bound," " south bound," etc. 



Train Signals. 

Many electrical devices have been tried to take the j^lace of the bell cord on 
trains but the latter still, almost exclusively, retains its place. 

The objections to the use of electrical devices for the purpose of permitting train 
men to communicate with the engineer have been that when, in the operation of such 
devices, " open circuits "have been used, frequent occurrences of short-circuits, whereby 
false signals have been turned in, have resulted; and, when closed circuits have been em- 
ployed, the rapid wasting of the battery necessitating constant attention, has mili- 
tated against the system. 

A system of train signaling known as the " Hart" train signal has been devised 
to obviate both of these objections. It is shown in Fig. 382. It is, in effect, a com- 
bination of the 0]3en and closed circuit systems of train signals. 

In the figure, c is a large signal bell of high resistance, c' is a small signal bell, 
or buzzer, of low resistance, both located in the cab of the engine, a is a switch, within 
easy reach of the engineer. B is the operating battery, which is placed under the 
engineer's seat. Press buttons, with double contacts, are located in each car, as at p, p, p, 
for operating the call bells. 

The system requires three wires, i, 2 and 3, as shown. Ordinarily, as in the fig- 
ure, the device is set for the open circuit arrangement. When thus set the depression 
of any of the buttons will complete a circuit, via the wires 2 and 3, througli the large 
bell c, ringing it. 

Should the circuits 2 and 3 become crossed or short-circuited at any point, as at 



x-, 



a circuit is formed through both the signal bells, but as the resistance of b 



IS 



5o8 



AMERICAN TELEGRAPHY. 



miicli less than that of c, the signal is only received on c', which indicates to the en- 
gineer the presence of trouble on the circuit. He then turns switch a, which puts the 
battery on closed circuit, via the wires i and 3, and cuts out bell c'. It also places the 
large bell c in the battery circuit, but the circuit formed by wires i and 3 shunts that 



FIG. 3S2. 




^i_ . 




1>^ 



± l_ 



and 3 
Thus 
be- 



"hart" train signal. 

bell. When, however, any of the buttons are depressed tlie shunt circuit i 
is opened, thereby permitting all the current to flow through the large bell c. 
this arrangement affords oj^portunity for the removal, at leism-e, of the " cross 
tween wires 2 and 3. 

The coupling used in connecting the wires between the cars has knife-edge sliding 
contacts. The "coupling-' is so arranged that when pulled apart it joins together the 
wires i and 3 and leaves wire 2 open. When the coupling is "made," wires i and ;^ 
and 2 pass, separately, through it. 



Since the foregoing was written (1892) some changes have been made in the 
arrangement and operation of the semaphores, and in the connections of the track 
circuits of many of the roads more recently equipped with block signaling apparatus. 
It is, of course, desirable, where jiossible, to dispense with the two- or three-inch iron 
pipe used to convey the compressed air in the pneumatic system, together with the 
expense of the com2:)ressor plant, etc. To this end different signal companies are 
availing of electric motors to bring the semaphore blades to safety against .gravity. 
Wooden poles for sustaining the semaphores are being generally displaced by hollow 
iron poles, in an enlarged base of which are placed the electric motor and battery. 
Iron rods within the poles communicate motion from the motor to the semaphores. 
In the Union Switch and Signal Company's system the iron rods R r' are raised by 
the engagement of a pivoted toe t (on the end of an arm a a' which extends from 
the lower end of the rod) with a knob on a sprocket-chain h li\ which is rotated 
vertically by the sprocket-wheel 5, which is operated by motor m, through wheel d 
and pinion^, as outlined in Fig. 382ft. In this figure the rods a a' are shown in 



MOTOR-OPERATED SEMAPHORES. 



508^ 



FIG. 382a. 



the danger position. AVhen a train passes out of a block the track relay is magnetized 
and attracts its armature, which closes the motor circuit, and the sprocket-wheels are 
rotated, raising arms a a', which brings the blades to safety position. AVhen brought 
to this position a pin on toe t engages with a catch c and holds the arms there. At 
the same time the motor circuit is 02)ened at contacts k by fingers/ on arms a. Toes t 
are controlled by a system of levers extending to the armatures of " catch '^ magnets 
e e, carried on arms a a'. When a train comes into a block the track relay is short- 
circuited, releasing the catch magnet, and the toe t is freed from the catch c, where- 
upon the blade is brought to danger by gravity, the vertical iron rods serving as a 
weight I'or that purpose. The dash pots D cushion the fall of the rods. Otherwise, 
the arrangement of circuits is practically similar to that shown in previous figures. 
In another system the iron rods are raised by a crank operated by the motor. 

In what is known as the wireless system the wires alongside the track are dis- 
pensed with, and the rails alone are utilized. In this system a combined neutral 
and polar relay is included in the track circuit. To each home signal rod is con- 
nected a pole-ch:inger J96', Fig. 382^, and as this signal goes to safety it operates the 
pole-changer in such manner that the battery of the 
track circuit behind is reversed, with the result 
that the polarized relay in that circuit moves over 
and opens the local circuit of the catch magnet of 
the distant signal at tliat point, allowing it to drop 
to display the caution signal. This operation of 
the polarized relay opens for an instant the neutral 
relay in the same circuit, and to prevent the neu- 
tral armatui-e from falling away at this time, a high 
resistance winding is placed on the catch magnet, 
which produces a slow release of the armature with 
the result desired. 

In the operation of the motor about 16 cells 
of caustic potash (Edison) battery are used, a cur- 
rent of 2 aniperes being required therefor. These 
cells have a capacity of 300 ampere hours, and 
should last, for this work, over two years witliout 
renewals on a road with fairly heavy traffic. The 
same battery is utilized for the catch magnets. 

The Hall Company have recently utilized gas 
at a pressure of 700 pounds, contained in a cylin- 
der placed beside the signal pole, to operate the 
blades in place of the pneumatic pressui'e de- 
scribed. The pressure is reduced to forty or fifty 

pounds at the valves controlled by the relays. The exhausted cylinders are replaced 
with newly charged ones at required intervals, and a charged cylinder is alwavs 
ready for use at the signal pole. 




MILLER CAB SIGN"AL SYSTEM. 

This is a system by which when two trains are within a certain prearranc^ed 
distance of each other a red incandescent lamp is automatically lighted in the cab of 
the rear engine. The electrical circuits, etc., for this system are shown in Fio-. -82/^;. 
Track batteries h h, track relays tt', and sections of insulated track are empToved'iis 
in the systems described, except that shorter insulated blocks e e' between the reo-u- 
lar blocks E e' are utilized. The circuits and apparatus on the locomotive cab are 



SoSd 



AMERICAN TELEGRAPHY. 



shown at c. One terminal t of these circuits is connected to the wheels of the 
engine, the other terminal t' is attached to one of the trucks of the tender, which 
truck is insulated, tt' and relays kk' each have two armatures, as indicated. The 
armatures of r r' are really pole-changers for batteries B b'. When no trains are on 
a block, relays tt' are closed by track batteries I) I), and at such times circuit of bat- 
tery B, for instance, is completed via lower armature of R to lower armature of T, to 
line wire a?, to upper armature of t' (t' being closed, as said), to and through relay r', 
to rail, to upper armature of R back to B. When an engine passes from a regular 



FIG. 3S2(^. 




X '" Y 

MILLER CAB SIGNAL. 



block to a short block, a circuit is provided from battery B or b' through the cab 
circuit. The direction of current at this time (assuming no engine on block ahead) 
is such that the armature A of a polarized lelay p is atti-acted to contact 6', completing 
a circuit through a white lamp av and a 5-cell battery s. When, however, an engine 
is on the block e, as at m, track relay t' is short-circuited and its armature contacts 
are open as in figure. When at this time also an engine passes from block e' to 
short block e', the wheel of locomotive and wheel of the tender together bridge, by 
means of terminals t t', the space between the said blocks, and ctirrent from b' 
traverses the cab circuit and' polarized relay p in an opposite diiection, and arma- 
ture A iS drawn against contact c', putting the red lamp R instead of white lamp w 
in circuit with battery s, as in figure. As long as the track ahead is clear, there- 
fore, the white light is continuously shown, and when the red light is shown it con- 
tinties to burn until the engine passes into a " clear " block, inasmuch as relay P 
remains on the contact on which it is last placed, until a current in reverse direction 
passes through it. Small battery K comes into play when the cab circuit to the track 
is broken. Normally its current passes through both coils of p equally, but when 
the circuit on either side is broken it passes through but one coil. When circuit 
to track is open the red light is shown. When circuit to small relay N" is broken 
that relay opens, opening both lamps at u, in either case calling for attention. 
Battery k, consisting of one cell, does not materially affect the operation of batteries 
b b'. The front insulated joints of the short blocks are set at such a distance apart 
that one or other rail maintains contact between the rail terminals t t' of the cab 
circuit as required. It will be observed that inasmuch as line wire x' is open at the 
lower armature of t', the line-wire circuit extending to and through the pole- 
changing relay to the right of r' (not shown in figure) will also be open, reversing its 
respective battery. In this way the block behind that on which a train is passing 
is also guarded. 



CHAPTER XXXI. 



OVERLAND TELEGRAPH WIRE. 

IRON AND HARD-DRAWN COPPER WIRE. — ^MANUFACTURE OF, ETC. — MECHANICAL TESTS 
AT FACTORY. CONDUCTIVITY TESTS. WIRE GAUGES, etC. 

Until within a few years past, iron was almost exclusively used for " overland '* 
telegraph wires, although it was well known that copper possessed electrical qualities far 
superior to iron. But the former high price of copper, added to inherent mechanical de- 
fects, combined, for years, to keep the latter metal out of the market, as a competitor of 
iron for such j^urposes. 

On this point the following language from an advertisement which appeared in 
an electrical periodical in 1868, may be quoted: " The superiority of copper as a con- 
ductor, over other metals, is well known, and but for its ductility rendering its perma- 
nent suspension in a pure state impracticable it would always have been used on tele- 
graph lines." 

The tensile strength of "soft" copper is about one-tenth that of iron. The ductility 
of soft copper is such that it becomes attenuated by its own weight between poles ; and 
having no elasticity, when elongated it has no tendency to resume its 
previous form. As an electrical conductor, copper is seven times better than iron. 
Again, self-induction is much less marked in copper than in iron; thus, apart from 
its superior conductivity, copper is better adapted for rapid signaling than iron. 

There is no comparison as between copper and iron in the matter of durability 
under exposure to, and without artificial protection from, the elements. Indeed, 
copper may be said to be, under ordinary atmospheric conditions, practically in- 
corrodible ; whereas it is known that iron even when protected by galvanizing, Avill 
succumb to the attacks of moisture and acids within ten or twelve years ; in some 
places in less than one year, as, for instance, in the vicinity of factories and railroad 
yards. Copper wire, exposed to the same conditions, simply takes on a coating of 
oxide and soot and is not further attacked. 

About 25 years ago the price of copper was at least 10 times greater than iron. 
More recently, however, the discovery and development of large deposits of compar- 
atively pure copper in this country conduced to a very material reduction of the cost 
of that metal, and a marked improvement in the manufacture of copper wire also soon 
followed. 

This improvement consisted in providing a wire known as "hard-drawn '' copper 
wire, of much greater purity, and one possessing a much higher tensile strength, thau 



5IO AMERICAN TELEGRAPHY. 

formerly ; although the added strength was obtained at the cost of pliability, which 
however, is not found to be seriously, if at all, detrimental. 

Prior to this improvement in the manufacture of copper wire, an eifort had been 
made to provide a telegraph wire which should have the strength of iron and much 
of the conductivity of copper. This resulted in the production cf a " compound " wire 
of iron or steel, and copper, many miles of which were strung in this country. In 
some instances the copper was placed over the iron wire by electrolytic deposition ; 
in others, by placing the copper, in strips, spirally around the steel core, the edges being 
run together so that the seams were not perceptible. 

Siliconized copper wire and phosphor-bronze wire were also introduced for the 
same purpose, but neither these, nor the compound wire, has, in this country, given any- 
thing like the satisfactory results obtained by the use of hard-drawn copper wire, 
which is doubtless explainable by the fact that the tensile strength given to hard- 
drawn copper wire, in the process of ^' drawing," having been found ample for the pur- 
pose of overland lines, it was evident that it would possess, practically, all the me- 
chanical advantagesof the compound wire and siliconized wire, with, in addition, su- 
perior electrical qualities. Its cost also, is probably below either of the foregoing 
mentioned wires. 

In some instances it was found that the durability of the compound wire was im- 
paired by a separation of the two metals. 

In silicious bronze wire, which is an alloy of copper and tin, the silicon is mainly 
used to aid in the removal of impurities, especially oxides and sub-oxides, and is not 
intended as a part of the alloy. The tensile strength of silicious bronze wire is some- 
what greater than that of hard-drawn copper, but the former appears to lose in conduc- 
tance as it gains in tensile strength. Silicious bronze wire has been somewhat exten- 
sively used in Europe, but in this country it has not been employed, other than ex- 
perimentally, for telegraph purposes. 



In the year 1884 the extensive employment of hard-drawn copper wire for over- 
land telegraph purposes was begun in this country. 

Although some misgivings were felt thatthe experiment, (for such its employment 
at first was conceded to be), would meet with failure, yet the advantages to be derived 
from its use, if it should prove successful, were so numerous, and decided, that the ex- 
periment was tried, and with such abundant success that to-day, in this country, it 
may be said that copper wire for overland telegraph lines is rapidly superseding iron. 
Indeed, iron wire is now, by some companies, only employed on new lines as a means 
of strengthening the lines. 

This successful use of copper has apparently shown that the high percentage of 
elongation always formerly called for in the specifications for telegraph wire was un- 
necessary; the percentage of elongation of hard-drawn copper wire not exceeding, on 
an average, 2.5 per cent, and in many cases falling below .5 of i per cent., without any 
marked prejudicial results following. 



OVERLAND TELEGRAPH WIRE. 



511 



THE MANUFACTURE OF IRON AND COPPER WIRE. 



The iron mostly used in the manufacture of wire is Swedish iron. It is brought 
to this country i:i the shape of pig iron, which, after passing through various processes 
to remove impurities is rolled into rods of any desired size. It is then prepared for 
the process of " drawing," by which it is made into wire. This preparation consists of 
fii*st thoro uglily cleansing the rods by washing, or "pickling," them in acids, after 
which they are covered with a flour paste, which is then dried hard by baking in an 
oven. The process of " drawing " consists of pulling the rods, while cold, by powerful 
machinery, through a steel die, in the manner indicated in Fig. ^S8. In the figure, 

D is the die, r is a revolv- 
ing drum, around which 
the wire is wound as it 
comes attenuated through 
tlie die. The rod is started 
through the die by filing 
the end for a short di* 
tance, when a clamp is 
attached to it. This clamp 
is fastened to a chain, and 



FIG. 383. 





WIRE DRAWING. 



the latter to the drum r. r is revolved by machinery not shown in the figure. The 
drawing is repeated until the wire is reduced to the desired size, a smaller die being 
used at each drawing. During the drawing process the wire becomes hardened and, 
consequently, it is necessary to anneal it between each drawing, and as the drawing 
wears off the flour coating, the wire must be re-coated between each drawing. It 
is said to be a curious fact that the wire in passing through the die does not come into 
contact with it at all,the flour acting also as a lubricant. 

The dies are made of the hardest obtainable steel or specially prepared cast iron. 

When iron wire has been drawn to the size required it is then annealed to the de- 
sired degree of softness. Each coil of the wire is then carefully inspected by the 
workmen to detect flaws or defects of any kind; coils containing which are rejected. 

The next process to which the iron is subjected is that of galvanizing. This con- 
sists of covering the wire with a thin coating of zinc. The object of this is to protect 
the iron from rusting, that is, from oxidizing. This the zinc does by combining with 
the oxygen of the air and thus forming a covering of oxide of zinc over the wire, which 
is not further assailed by air, unless in the presence of a gas, such as sulphuric acid 
gas, set free from burning coal, etc., when the acid combines with the oxide of zinc, 
forming sulphate of zinc. The latter, being soluble in water, is soon washed oft' the 
wire, leaving the iron to be quickly attacked by the oxygen of the air, and in a short 
time corroded. 

It is very essential that the surface of the wire should be chemically free from 
all impurities, such as sand, scales, cinder, oxides, etc, before it is galvanized, otherwise 
the zinc will not properly adhere to the iron. To insure this essential, the wire is again 
"pickled" by immersion in a vat containing a solution of dihite sulphuric acid, for 
from six to twenty-four hours, after wliich it is flushed in water to remove the acid. 



512 AMERICAN TELEGRAPHY. 

To Still further cleanse the iron it is immersed in muriatic acid which removes oxides 
that form (after the pickling process) when the wire is exposed to the air. 

The act of galvanizing the iron wire consists in momentarily immersing the wire 
in a bath of molten zinc. One of the methods employed for this purpose is shown 
in Fig. 384. The wire is brought on reels to the vicinity of a sort of oven k, 

FIG. 384. 




GALVANIZING IRON WIRE. 



which has, running through it, horizontally, a number of fire brick tubes, which are 
kept at a white heat by a furnace f, extending under the oven, m is a trough con- 
taining a solution of muriatic acid, g is a bath of molten zinc. The zinc is kept " boil- 
ing " by a furnace under the trough. Several reels of wire may be run simultaneously 
through the tubes of K. The wire in passing through these tubes at a mo^lerate rate 
of speed becomes heated to redness. On its exit from its tube the wire fulls into 
the acid, where all traces of grease, oxides, etc., are removed, and the next moment 
he wire passes through the molten zinc and emerges therefrom galvanized. 

The wires are automatically wound on the reels i, j, after leaving the zinc bath. 

The iron being heated to a high temperature in passing thro?igh the tubes any 
acid that may adhej'e in j)assing through the solution is at once evaporated and the 
distance between the acid vat m and the zinc bath g is so short that but little time 
is given for the iron to oxidize. It is very important that the zinc should be kept at 
a fixed temperature ; the best results are said to be obtained with a bath heated to 
about 740° F. 

The effectiveness /)f the galvanizing is tested, generally, as follows: Apiece of 
the galvanized wire is immersed for one minute in a saturated solution of sulphate of 
copper. The affinity of the sulphuric acid of the salt for zinc is well known. The 
effect of this immersion is that some of the zinc combines with the sulphuric acid of 
the sul23hate setting free copper. When iron is immersed in such a solution the cop- 
per is set free on the iron. The foregoing action is repeated three or four times, as 
may be called for in specifications. If at the end of the fourth immersion there is 
no appearance of a copper deposit on the wire thus repeatedly immersed, but, on the 
contrary, it remains black, as after the first immersion, the galvanizing may be con- 
sidered effective. The j^resence of a copper deposit would indicate that the iron had 
become exposed and that,consequently,the galvanizing was imperfect. 

Copper rods are prepared for drawing into wire in the same general way as iron. 
The manner of drawing the copper rods into wire and that wire into still finer wire is 



OVERLAND TELEGRAPH WIRE. 5 13 

also similar to that by which iron is "drawn." When, however, the copper wire is 
intended to have a high tensile strength it is not annealed so frequently between the 
different drawings as in the case of iron. 

Experiments have shown that the ductility of copper wire decreases as its tensile 
strength increases, but the experiments were not continued to an extent sufficient to 
show the exact ratio. A specimen of copper wire, thoroughly annealed, .128 inch in 
diameter, was found to have a tensile strength of 330 lbs., and elongated 36 per cent. 
A sample of the same wire, on being drawn twice, to reduce its diameter to .104 inch, 
had a tensile strength of 330 lbs., and elongated 23 per cent. Another specimen, 
from the same piece, on being drawn thrice to bring it to the same diameter, namely 
.104 inch, was found to have a tensile strength of 415 lbs. and elongated but 3 per 
cent. Still another specimen from the same wire, drawn four times to reduce it to 
.104 inch, had a tensile strength of over 550 lbs. and elongated but i percent. 
The average of a number of like experiments indicated that, in obtaining an elonga- 
tion of 2.5 percent, to 3 per cent., a reduction of 130 to 140 lbs. in the tensile strength 
would follow. 

The term "hard drawn" is applied to distinguish the unannealed from the an- 
nealed copper wire ; the only difference between soft copper wire and hard drawn 
copper wire being that one is annealed after drawing while the other is not. The 
process of drawing the wire through the die forms a thin, hard, polished crust, 
or shell, not exceeding the one thousandth of an inch in thickness, over the wire. In- 
side of this crust the metal is, seemingly, comparatively soft. The tensile strength of 
hard drawn copper wire appears to rest in this outside shell, for the slightest inden- 
tation made around the circumference of the shell with a sharp instrument will at 
once lower its breaking strain ; and while, with an undented surface, the copper wire 
may withstand 5 or 6 bends on itself, with such a dent it will break in one bend. 

WIRE JOINTING AT FACTORY. — At One time it was quite customary to require, in 
specifications for telegraph wire, that the wire should be delivered in continuous lengths 
of one halt' mile or more, without joints. This was when it was the habit to make the 
large twist joint (shown Fig. 420). In ordering hard drawn copper, also, the same 
requirement was inserted; the "sleeve " joint being then used. The objections to 
such joints were that the tensile strength at those points was considerably less than 
that of the main wire ; that they retarded the work of uncoiling the wire in the act of 
stringing, and that, when the wires were strung, the joints frequently, by engaging 
with parallel wires, caused steady crosses, which would otherwise have been but mo- 
mentary wind crosses. Hence, it was very desirable to reduce the total number of such 
joints, to a minimum. 

As it is not an uncommon occurrence for wire to break in the act of drawing, the 
matter of jointing such broken wires in such a manner as to avoid the objections re- 
ferred to, was one which received much attention from the manufacturers, and various 
attempts were made to weld the joint, mechanically, without materially increasing its 
bulk, or decreasing its tensile strength; but only with indifferent success. Of late, 
however, electric welding has been resorted to, for this purpose, with marked satisfac- 
tory results. In making joints, or welds, by this process, the ends of the broken wires 
are broughx together, and are fastened to separate clamps. Wires connected with a- 
dynamo machine are brought to these clamps, and a very strong current is then caused 
to pass through the tips of the broken wires, which speedily produces a heat sufficient 
to form a perfect union between them. For ordinary telegraph wire the time of ap- 
plication of the current is but a fraction of a second, but the time of application of the 
current, the extent of the wire exposed between the clamps, and the pressure with which 
the ends are brought together, varies with different wires. Wolds made in this wav 
have scarcely a perceptible burr, and tests have shown that the tensile strengtxi of the 
weld is practically similar to that of the wire proper. 



514 american telegraphy. 

Mechanical Tests of Telegraph Wire. 

The purchasers of copper and iron wire almost invariably have it inspected by 
a representative, at the factory, in order to ascertain before acceptance of the wire, 
whether it meets the requirements of the specifications. 

The mechanical tests to which iron and copper wire are subjected and the man- 
ner in which the tests are made are practically as follows: 

TESTS FOR GAUGE OR DIAMETER. — The diameter of the wire is generally stated 
in the specifications as so many mils. 

In drawing lotig lengths of wire through the dies in the manner previously de- 
scribed, it very seldom happens that the wire is of exactly uniform diameter 
throughout. It is generally slightly thicker near the ends than in the middle. This 
is supposed to be due to a gradual clogging up of the die hole at the beginning of 
the drawing, which clogging seems gradually to disappear and thus the die hole re- 
sumes its normal size towards the end of the drawing. The disparity, however, be- 
tween the ends and the middle of the drawing is not ordinarily very great, not 
amounting to over i or 2 mils, at most. But, to guard against a too marked discrep- 
ancy between the various parts of the wire, the coils are " gauged " at the ends and 
center by means of a " micrometer," or other suitable gauge. 

WIRE GAUGES. — 111 this countiy and Great Britain the diameter of wires is meas- 
ured in mils. The diameter of insulation of wires in "32ds" of an inch. There 
are nearl}^ 31.2 mils in the -3^2 o^ ^1^ inch. 

In order to distinguish the different sizes of wires it has been customary to desig- 
nate wires of specified diameters by a given number of an arbitrary gauge. Thus 
a wire having a diameter of .083 inch, that is, 8;^ mils, would be No. 14 
Birmingham w^ire gauge, or b.w.g. One having a diameter of .080 inch would be 
No. 12 Brown and Sharj), or B and S, gauge, and wires ranging from a few mils to an 
inch in diameter, have been classified in those "gauges,'' in numbers ranging from i 
nought (o), 2 nought (00) 3 nought (000) etc,, up to 36 and 38. The smallest wires 
being alloted the highest numbers of the gauge, and vice versa, {see wire tables). 

Since the numbers of the gauge only include wires of 40 or 42 different diameters, 
it is plain there Avill be many sizes of wires in use, and necessary, which do not coincide 
with any of the many arbitrary gauges. The various wire gauges also differ very 
materially from each other and much confusion is, consequently, occasioned. 

These causes have led many large users of wire to designate the size of the wire 
desired by its diameter in mils, or by the square of the diimeter in mils, which is 
termed circular mils, or by its sectional area in square inches. Sometimes by its weight 
per mile, disregarding altogether any reference to the arbitrary wire gauges. 

For instance, if a wire measuring St, mils in diameter is desired, it may either be 
designated as a wire 83 mils diameter; or as one of .005567 square inches, cross section. 

Instruments for measuring the diameter of wires, or for at once ascertaining the 
gauge of a wire in terms of some one of the numerous " standard " wire gauges, are 
also termed " wire gauges." 

A specimen of one of the latter is shown in Fig. 385. It is known as the "Amer- 
ican standard wire gauge." It consists of a thin, flat, circular piece of metal, having 



MECHANICAL TESTS OF TELEGRAPH WIRE. 



5^5 



indentations, or slots, on its periphery, as shown. Each of those indentations is num- 
bered, as in the figure. The apertures of the various indentations are of a size corres- 
ponding with the diameter of the wire of a certain number of the Brown and Sharp 
Avii-e gauge. Consequently, when it is desired to know the gauge of a wire, in terms 
of the Brown and Siiarp gauge, without being any wiser as to the actual diameter of 



FIG. 385. 



the wire, unless by reference to a Brown 
and Sbarj) wire gauge table, the said wire 
is placed sideways into the apertures, or 
openings, on the edge of the wire, as at x 
until it reaches tbe aperture closely fitting 
it, when reference to the figure stamped on 
the disc will indicate the number of the wire 
in the Brown and Sharp gauge. 

Fig. 386 represents a " micrometer," or 
"pocket," wire gauge. It is constructed 
to measure from the one thousandth of an 
,iiich up to its maximum capacity; which 
may be \ inch, one inch, or more. The 
manner of its construction and use is as fol- 
lows: The instrument is made of polished 
steel The screw s is attached to the milled 
cap M, at the point x. c is a sleeve, over s, also rigidly attached to the cap 
M. The left end of sleeve c is bevelled, as shown, and on this beveled edge 25 hori- 
zontal, short, equal divisions are cut. r and e are extensions of the U-shaped metal piece 

p. A hole having a thread suitable for 
the screw s, runs lengthwise through e 
and e'. a number of vertical divisions are 
cut, as shown, on the extension e ; also 
one horizontal line. When the sci'ew s is 
screwed into the thread until it meets the 
extension r the sleeve c covers the extension 
E, up to the perpendiculrtr mark, o. TJie 




FIG. 386. 




I ' fc^.<^*--,^-— -^ 




rrrrrlk ^ ^. 


— H'>: 




threads of the screw are so arranged that 



MICKOMErER WIRE GAUGE. 



in one revolution of the screw it moves to 
or from the extension F,tlie .025 of an inch, that is, the one fortieth of an inch. The 
perpendicular marks to the right of zero on e are so arranged that, starting from zero, 
each of them measures one complete revolution of the scrcAv. Thus, when the screw 
has made one revolution from f the zero mark on tlie sleeve c will be opposite the 
horizontal mark on e, and the bevelled edge of c will be 0])posite the first perpendic- 
ular mark to the right of zero, on e. Consequently, a wire which would fit into the 
opening between e and r, when zero on the bevelled ii(\.<^^ of c rests directly over the 
first vertical mark from zero, on e, will have a diameter of 25 mils. Each of the other 
perpendicular marks on e will also indicate that the screw has travelled an additional 25 
mils. Now, since the bevelled edge of c travels with the screw, being rigidly attach- 
ed to it at M, any fraction of the 25 mils between the veitical marks on e 



5i6 



AMERICAN TELEGRAPHY. 



will be indicated by the horizontal marks on the edge of c. For instance, in the fig- 
ure there are five perpendicular marks exposed. Therefore, up to the mark under 
the figure i, on e, which stands for loo mils, the screw will have made four revolutions, 
and the space between that mark and the bevelled edge indicates that it has per- 
formed part of another revolution, and the extent of that part of a revolution is shown 
to be ^f , since the tenth division on the bevelled edge is opposite the horizontal mark 
on E. 

In other words, a wire which would fit snugly into the space between s and f 
while the gauge is in the position stated, would have a diameter of one hundred and 
ten one thousandths of an inch. 



FIG. 387. 



TEST FOE TENSILE STRENGTH OR BREAKING STEAIN. A Sample, about 1 6 incheS 

in length, is taken from the 
ends of a coil. Each bundle, 
or coil, of wire may be 
tested, if desired, but as this 
would be a very arduous task 
in the case of very large 
lots one coil in about ten may 
be selected. The specimens 
of wire actually tested may 
be any determined length; 
generally a piece lo inches 
long is specified. 

One form of apparatus 
for making this test is shown 
in Fig. 387. It consists of 
a beam and scales b, suitably 
supported at .r; a screw s and 
a means for turning the 
screw up or down. Some- 
times this consists of a crank; 
at other times a belt and 
pulley is provided, as shown 
in the figure. The wire w to 
be tested is placed in the 
jawsy and/'. Care must be 
taken to see that, while the 

TESTING FOR TENSILE STRENGTH. jaWS liold thC WirC Hgldly 

they do not cut it in anyway. The exact length of wire to be tested should be placed 
in the jaws so that when everything is ready for the test the jaws of the machine will be 
just 10 inches apart. The machine should then be slowly started and always at as 
nearly a uniform rate of speed as possible, for each sample tested. The screw in de- 
scending puts a pull on the wire and this tends to raise the scale end of the beam, 
just as if a weiglit had been attached to the jaw j'. To meet this pull and to bring 




MECHANICAL TESTS OF TELEGRAPH WIRE. 



517 



the beam back to a balance the bob b is moved along the scale. This is continued 
until the wire breaks, when the number of pounds indicated on the scale is noted. 
This will be the tensile strength of the sample. 

TEST FOR ELONGATION. — The test for elongation or, in other words, the stretch- 
ing qualities of the wire, is partly arranged for while the" wire is in position for 
testing for breaking strain. The wire just outside of the jaws having been carefully 
marked -vi-ith a pencil^ after the wire has broken and its breaking strain has been test- 
ed, the fractured ends of the wire are placed as closely together as possible and the 
le-Tigth cf the wire from mark to mark is measured. From this measurement the per- 
centage of elongation may be readily calculated. For example, if, after breaking, 
the length of the wire is found to be lo.i inches, the percentage of elongation would 
te I per cent. 

TESTS FOR DUCTILITY. — Tests for ductillty are made in at least two ways. One 
of these is illustrated in Fig. 2)^'^- Iii this v is a stationary vice, supported on a table. 
v' is a vice, or clutch, capable of being rotated by the wheel, or crank K. The wire 
w, generally six inches in length, is placed, 
as shown, in the jaws of the vices, which 
are then tightened. In some cases a 
streak of ink is placed on the upper surface 
of the wire. The vice v' is then rotated by 
means of the crank k, at a uniform rate 
of speed, until the wire breaks. The num- 
ber of twists which the wire has withstood 
will have been equal to the number of 
complete turns of the wheel, or the 
twists may be ascertained by counting the spiral now formed by the ink streak. 

This test is sometimes varied by bending the wire back and forth upon itself. 
For copper this test is jjerhaps more valuable than the twist test, since it shows how 
many bends and kinks it is likely to withstand without breaking. For making the 
latter test a device somewhat resembling a lemon squeezer, without the receptacle 
for the lemon, has been used. The " squeezer " is first laid open, when the wire is 
placed upon it and clasped there. The device is then closed and opened until the 
wire breaks. (See specifictions for wire.) 




DUCTILITY TEST. 



Wire Testing For Resistance and Conductivity. 

In the natural state, iron and copper are found, mixed more or less, with oxides 
carbon, arsenicjphosphorous, etc., to remove which impurities is the object of the various 
refining, smelting and hammering processes to which the metals are subjected, but not 
always entirely successfully, by the manufactiu-ers. 

As stated elsewhere herein, electrical resistance is the converse, or reciprocal, of 
conductance. Whatever, therefore, tends to increase the conductance, diminishes the 



5l8 AMERICAN TELEGRAPHY. 

resistance of a conductor, and contrariwise. A very small percentage of either of the 
named, or other impurities, in iron or copper, has a marked effect in reducing tlie elec- 
trical conductance of these metals. 

Matthiessen and Holzman, who examined particularly the effect of foreign sub- 
stances in copper, placing the conductivity of silver at loo, and hard drawn copper at 
93.08, found the percentage conductivity of 

Copper containing 2.5 per cent, phosphorous to be 7.24 

" " .48 per cent, iron " 34.56 

" " traces arsenic " 5 7-8o 

" *' 1.22 per cent, silver " 86.91 

" " 3.5 per cent gold '* 65.36 

from which it is seen that a very small ]K^rcentage of foreign substance affects largely 
the conductivity of copper, even when the foreign substance is, itself, a better conductor 
than copper. Iron and other conductors are affected analogously. 

It also happens, sometimes, that the conductivity of conductors is decreased by 
imperfect treatment in the course of wire drawing, etc., and from both of these causes, 
namely, the presence of impurities in the metals and imperfect manufacture, occasional 
batches of defective wire result. 

To detect any wire that may be defective, as well as to ascertain the exact specific 
conductivity of the wire, electrical tests are mainly resorted to. The terms, specific con- 
ductivity and specific resistance of a material, refer, of com-se, to the conductivity and resis- 
tance of that material, as compared with some standard ; as analogously, we speak of the 
specific gravity of a substance — meaning its gravity as compared with an equal bulk 
of water, etc. In the case of copper wire the standard is pure copper, which is con- 
sidered as having a conductivity of 100. The specifications for copper wire intended 
for electrical purposes, often referred to as commercial copper, generally call for a 
material having a specific conductivity of 96 or 98, or a conductivity equal to 96 per 
cent, or 98 per cent, of that of pure copper. For example, if it is known that a wire of 
pure copper of a given diameter has a resistance of 5.76 ohms per mile, at 75^ F.,a 
commercial copper wire of the same diameter, required to have a conductivity equal to 
96 per cent of pure copper, should have a resistance of 6 ohms, per mile, at the same 
temperature. 

This will be clear when it is considered that, conductance being the converse, or re- 
ciprocal of resistance, the conductance of the pure copper wire will be -g-^y^, while that of 
the commercial wire is but ^. It is then apparent that |- is 96 per cent, of -^}j-q- 

For the purpose of ascertaining the percentage conductivity of wires, samples of 
the wires, one-fiftieth or one-hundredth of a mile in length, are usually chosen and 
tested for resistance ; a method frequently employed being that of the Wheatstone 
bridge. The lengths mentioned are chosen to facilitate the calculations, and this is 
evidently an object when hundreds of samples may have to be tested. 

The Wheatstone bridge*and other apparatus, and the connections for such tests, 
are outlined in Fig. 389. In the figure r and e' are the adjustable arms of the bridge. 
B is the adjustable rheostat, with coils ranging from i ohm to 4,000 ohms. t and t' 
are the points to be brought to equal potentials for a balance, x is the unknown re- 
sistance, in this case the wire to be tested, which is connected at t' and w,and is coiled 

* Fully described in Chapter YIII. 



WIRE TESTING. 



519 



around an insulated support d. b' is a battery. Keys k k' are inserted in the galvano- 
meter and battery circuits, respectively, g is a Thomson reflecting galvanometer. If 
very accurate results are not required a detector or tangent galvanometer may be used 
in the bridge wire. The Thomson reflecting galvanometer is described in a separate 
chapter. It may be added here that the beam of light should rest on the zero of the 
scale when no current is flowing through its coils. It may be brought to zero by 
manipulating the directing magnet m, for which purpose an endless screw is conveni- 
ently jDrovided on the instrument. The sensitiveness of the needle to currents in the 
coil may be increased by raising the magnet m, and decreased by lowering it. 

FIG. 389. 




W^ 



INF i 




For measuring pieces of wire of very low resistance, the 10,000 ohm coil of e, and 
the 10 ohm coil of r' of the bridge arms are used. 'Iliis, of course, gives a ratio of 
1,000 to I. Or a ratio of 100 to i may be obtained by using the 1,000 ohm coil in R, 
and the 10 ohm coil in e'. In making the test the wire is coiled around the support 
D, care being taken not to permit the coils to touch each otlier. If the approximate re- 
sistance of the wire to be tested is known, the ratio of the arms e, e', may be arranged 
accordingly, and a resistance may at once be placed in b, equal to the approximate re- 
sistance. The depression of k' places the battery in circuit, that of k the galvanometer. 
Key k' is depressed first and then key k. A shunt around the galvanometer may be 
used if, at first, the deflection is too large. The keys are depressed at intervals, and 
resistance inserted in b until a balance is seciu-ed at t, t', that is, until the galvano- 
m.eter is not affected by the depression of the keys. If the approximate resistance is 
not known, it must be ascertained by experiment; by inserting and removing resistance 
until a balance is obtained. In the latter case the result is facilitated by '' shunting" 
the galvanometer with the \ shunt, until an approximate resistance is found. 



520 AMERICAN TELEGRAPHY. 

An instance of the practical utility of this testing arrangement is to be found when 
measuring the one-hundredth part of a mile of wire, (the ratio of the arms r, r' of the 
bridge being as i,ooo to lo, or as loo to i), in which case the resistance inserted in the 
rheostat b to procure a balance, while, in reality, one hundred times greater than the 
resistance of the piece of wire x, is, at the same time, the actual resistance of one mile 
of the same size of wire. To explain : Assuming that the resistance thus inserted in b 
is 10 ohms. The resistance of x is, therefore, one hundredth of this, namely -^ ohm. 
But, as X is only the one hundredth part of a mile in length, it is necessary to multiply 
^^Q- by I GO to get the resistance for one mile, which, of course, brings the figures back 
to 10 ohms. The resistance, per mile, having been thus ascertained, the specific con- 
ductivity of the wiic may be calculated by a comparison of its resistance with that of 
pure copper or iron wire, as the case may be. 

To get the best results in the foregoing tests the resistance of the galvanometer 
coils should be very low, and a battery of one or two cells, having low internal resis- 
tance, should be used. Two gravity cells, joined up in multiple, as shown in Fig. 394, 
will, as a rule, suffice for such tests. 

If the sample to be tested is not connected directly to the bridge box terminals, the 
connecting wires should be very large, in order that their resistance may be neglected, 
or, otherwise, their resistance should be ascertained, and deducted from the results of 
tests. 

When it is impossible to get an exact balance by the aid of any of the coils of the 
rheostat b, the following plan may be availed of. 

Suppose that, with 9 ohms in the adjustable rheostat, and with the arms of the 
bridge even, a deflection of 10 divisions to the right on the scale is obtained, and that, 
with 10 ohms, a deflection of 20 divisions, to the left. In that case, the resistance of 
the wire x is, evidently, more than 9 ohms, and less than 10 ohms, that is, it is \% of r.n 
ohm, in excess of 9 ohms, or |-§- of an ohm less than 10 ohms. In other words, the re- 
sistance is 9 ohms and -J^ of an ohm, or 9^ ohm. 

If the arms of the bridge should be uneven, the resistance in b must be divided by 
the proper divisor. For instance, if the ratio be 100 to i, the actual resistance of x 
would be, in the case just cited, .0933 ohm. 

CORRECTIONS FOR TEMPERATURE. The clcctrical rcsistancc of metal conductors 
varies with the temperature of the metal; the resistance increasing as the temperature 
rises, and vice versa. It is, therefore, important to note the temperature of the room 
at the time of testing. The test should not be made until the wire has been in the 
test room long enough to acquire its temperature. The variation of resistance, due to 
temperature, is not the same for all conductors, but is approximately so for pure 
metals. 

Matthiessen found by experiment that the resistance of pure copper increased at 
the rate of about xoVoo" ^^^ ^^^^ degree Fahrenheit increase of temperature. Thus, 
if a wire at 6c° F. has a resistance of 6 ohms, at 61° it will measure 6 + (6 X .0021) 
ohms =: 6.0126 ohms. The same wire at 62° F. will measure 6.0126 + (6.0126 X 
.0021) = 6.025 ohms, and, at 63° F. the sa^ne wire will measure 6.025 + (6.025 X 
.0021) = 6.038 ohms; the rate of increase, it will be seen, and as pointed out by 
Culley, being similar to that of money at compound interest, the degrees f, cori-es 



WIRE TESTING. 



52 



ponding to the number of years in tlie former. As it would be onerous to calculate, 
in this way, the corrections for variations of temperature, tables of co-efficients, or 
multipliers, are made up, based upon the increase in unit resistance for a certain num- 
ber of degrees variation of temperature. For example, the increase of resistance for 
I ohm for I ° F. increase temperature would be 1.002 1 ; for 2°, 1.0021 + (1.0021 X 
.0021), which is equal to 1.0021 X 1.0021, or, 1.0021 squared. For 3°, the increase 
would be 1.0021^, and so on. Consequently, since the increase for i ohm is as stated, 
the corrected resistance for, say, 3° increase of temperature, in a wire measuring 6 
ohms, would be 6 X 1.002 1^ = 6.038 ohms. 

A table for a variation of 20° Fahrenheit is subjoined. 

CO-EFFICIENTS FOR CORRECTIONS FOR TEMPERATURE. 



1° 






1. 0021 












•9979 


2° 






1.0042 












•9958 


3° 






1.0064 












•9937 


4° 






1.0085 












.9916 


5^ 






I.OI06 












•9895 


60 






I.O128 












.9874 


f 






1.0149 












•9853 


8<> 






1. 0170 












.9832 


9" 






1-0193 












.9811 


10^ 






1. 0214 












.9790 


11° 






1.0236 












.9769 


I2<' 






1.0258 












•9749 


13° 






1.0280 












.9728 


14^ 






1. 0301 












.9708 


15^ 






1.0323 


ft 










.9689 


16° 






1-0345 












.9666 


17° 






1.0367 












.9646 


18° 






1.0389 












.9626 


19- 






I.0411 












.9605 


20^ 






1-0433 












•9585 


To correct 


from low to high temperature take the co-efficient 


in the left hand column 


opposite the degrees 


representing th 


e difference between 


. the observed resistance and that to 


which it is desired to correct to, and multi- 


ply the observed resistance by that 


co-efficient. 


To correct from 


high 


to low 


apply 


same 


; rule 


but using right 



hand column of co-efficients. 

As the resistance increases with increased temperature and decreases with de- 
creased temperature the left hand column of figures should be used when it is desired 
to correct from a lower to a higher temperature; if from a hio-her to a lower tem- 
perature the right hand column should be used. 

The right hand column of figures represents merely tlie " reciprocals " of those 
on the left, advantage being taken of tlve fact tliat, to multiply by the reciprocal of 
a number is equivalent to dividing by that number. 

Where strict accuracy is not required tlie following formula will o-ive an approx- 
imately correct co-efficient for commercial copper, namely : I + (.0021 X T°) where 



522 AMERICAN TELEGRAPHY. 

T° is the number of degrees Fahrenheit between the observed temperature and that 
to which it is desired to correct the resistance for temperature. 

If it is desired to correct the observed resistance to a higher temperature, the 
observed resistance should be multiplied by tbe co-efficient; if from a higher to a low- 
er temperature the observed resistance should be divided by the co-efficient. Tlius 
assuming a certain wire to have at 6o°F. a resistance of 6 ohms, and that it is desired 
to correct it to 70° F. The difference in degrees being 10 , the co-efficient would be 
I -|- (.0021 X 10 ) — 1.021; hence, the corrected resistance of the wire in question 
would be 6 X 1.02 1 ■=■ 6.126 ohms. Similarly the co-efficient for any ordinary 
number of degrees variation of temperature may be obtained. 

WEIGHT PER MILE OHM. — The Standard for telegraph and telephone wires in this 
country is a cylindrical wire, one mile in length, measuring one ohm, at 60° F. Thus 
a standard wire of pure copper would weigh, virtually, 871.177 lbs.; a standard wire oi 
pure iron about 4,000. This is termed tlie ohm mile. From this is derived the 
expression "weight per mile ohm," or "pound-mile-ohm," a term applied to the ])roduct 
of the weight, per mile, of a wire, multiplied by its resistance, per mile It is a useful terra 
in several respects. Thus having obtained a '• standard " pound-mile-ohm, at a 
given temperature, for pure iron or copper, it affords a convenient means for calculat- 
ing the percentage conductivity of a "commercial" wire of either metal. For example. 
If the pound-mile-ohm for pure copper be 871.177 at 60° F., and it is found that 
the pound-mile-ohm of a commercial copper wire is 888.59, ^^ the same wmperature, 

its percentao:e conductivitv will be 98. That is, ' ' '' — = 984-. 

Again. Knowing the pound-mile-ohm of a metal, and having the resistance of a 
wire of that metal, per mile, its weight, per mile, may i-eadily be determined by di- 
viding the pound-mile-ohm of the same metal, by the resistance, per mile. Oj-, it' the 
weight, i)er mile, is known, the resistance, per mile, may be ascertained by dividing 
the pound-mile-ohm by the weight, per mile. 

For instance, if a wire of 98 per cent, commercial copper weighs 200 Jbs., per 
mile, its resistance, per mile, will be -8-|§^5.9 — 4,44 ohms. Or, if tlie resistance, per 
mile, of a similar wire is 4.44, i^er mile, its weight, per mile, vvill be -^f.^-j^ = 
200 lbs. 

Again, in testing wire, the weight of the sample or coil may be careful!}^ ascer- 
tained and from that, its weight, per mile, may be calculated, from whicli the 
''weight per mile ohm " may be obtained, and from that the percentage conductivity. 
Otherwise the resistance of the wire would first have to be compared with a pure 
copper or iron wire of the same weight or diameter, per mile, to ascertain the conduc- 
tivity. 

Numerous experiments have been made to determine the exact value of the 
practical unit of resistance, the ohm. For many years the unit known as the B. A., or 
British Association unit, was extensively employed. Subsequently another determina- 
tion of the ohm was made by a committee, authorized by the Paris Congress of Elec- 
tricians, the result of whose work was the introduction of a unit, termed the Legal 
ohm, having a value 1.12 per cent, higher than that of the B, A. ohm. In the fore- 



WIRE TESTING. 523 

going remarks concerning " weight per mile ohm," the B. A. ohm is assumed. The 
*' ohm mile" for pure copper would be, in legal ohms, 861.142 lbs., approximately. 
Standard resistance boxes are made up in value of legal or B. A. ohms, as desired; the 
boxes being stamped accordingly. 



IRON AND SI EEL LINE WIRE. — In vicw of the forcgoing explanations the following 
trade terms and items concerning iron and steel wire, compiled from Washburn and 
Moen's pampiilet, will be readily understood. 

I. ExiRA-l>EST Best. 

IT. Best Best 

III. Best. 

1. ''i5'jc//'^-^<fj-/^<?^/," I^y improved continuous processes from very best iron. 
This grade stands highest of any known telegraph wire in conductance, with a "weight 
per mile ohm" of from 4,600 to 5,100 lbs. Very uniform in quality, pure, very tough 
and pliable. 

2. "- Best Besty Less uniform and tough than the above named, but stands a 
good mechanical test. "Weight per mile ohm/' 5,500 to 5,800 lbs. Is largely used 
by some telegraph companies, and in railway telegraph service. 

3. "^^j-/." A term almost indis'n-iminately applied to the lower grades of wire 
designed for electric service. A harder and less pliable wire, about 6,500 weight per 
mile ohm. 

4. " 6'/<?^/," or homogenous metal, more expressly designed for short-line tele- 
phone service, where a measure of conductivity can be exchanged for greater tensile 
strength in a very light, strong wire, 6,600 to 7,000 weight per mile ohm. 

The first named, or " Extra-best best,'' is almost exclusively employed in the best 
telegraph service, though there are instances in line construction where long spans 
call for a wire of greater tensile test strength, and steel is employed for that purpose. 

The standard breaking strain of superior galvanized wire is two and one- half times 
its weight per mile. 



CHAPTER XXXII. 

Underground Conduits. — Underground, and River and Harbor 

Telegraph Cables, Etc. 



CABLE TESTI - G. ELECTRO-MECHANICAL METHODS OF LOCATING FAULTS IN CABLES., ETC. 



UNDERGROUND CONDUITS FOR CABLES. — The evident desideratum in an under- 
ground conduit system is the maintenance of the insulation of the conductors placed 
therein. 

This may be accomplished in two general ways. iSTamely: By using,for the con- 
ductors, an insulating covering impervious to gases and moisture; the duct to 
serve simply as a mechanical protection for the covering. Or, by the employment of 
bare conductors, or an insulating covering of inferior quality, in a conduit which 
shall be so constructed and maintained as to provide conditions under which the in- 
sulation of the conductors shall remain intact. 

The first method requires the construction of a substantial conduit, but one not 
necessarily water or gas proof. The second requires the construction and maintenance 
of a conduit which shall be gas and moisture proof — at least the latter. 

It thus becomes a question as to whether the expense shall be incurred of pro- 
viding a conductor insulated with a gas and waterproof material; or of providing 
and maintaining a conduit, moisture and gas proof. 

Of the underground electrical conduits whicli are now in active operition, there 
are at least two types. The " solid" conduit and the " drawing in and out" conduit. 

The "Edison"' underground conduit is an instance of a solid conduit. It 
consists of a wrought iron pipe, in which, copper rods, forming the conductors, are 
placed. These conductors are wound with rope, and the pipe is filled with an insa- 
lating compound of resin, paraftin, linseed oil, and Trinidad asphaltum. These iron 
pipes are laid directly in the earth. Once laid in the trench the conductors are prac- 
tically immovable and can only be got at by digging down to the pipe. Terminal 
boxes are, however, employed at stated intervals along the route of the conduit 
by means of which direct access may be had to the conductors, by the removal 
of a cover. 

The drawing in and out conduit generally consists of wrought or cast iron, wood- 
en or cement pipes, placed in trenches. The diameter of the pipes is generally from 
two to three inches. The method commonly adopted in laying the iron pipes is as 
follows; The bottom of the trench is. first levelled to grade; planks are then set 

524 



UNDERGROUND CONDUITS. 



525 



against the side of the trench to sustain it. A layer of concrete is then laid and ram- 
med in the bottom of the trench. On this is placed a row of iron pipes, (if more than 
one duct is required), next a layer of concrete, then another row of pipes, and so on, 
until the desired number of pipes is laid. In order to add strength to the mass and 
to protect the ducts from mechanical injury, the concrete is applied more thickly on 
the bottom, top and sides of tiie conduits, than between the pipes. There is placed, 
over all, a two-inch yellow pine plankijig, heavily creosoted, to further protect the 
conduits against injury from picks, crow bars, etc., in the event of future excavations 
in the streets. 

Tiie iron pipes are joined end to end by a coupling screw joint with a tapering, 
or vanishing, thread. 

FIG. 390. 




Access is had to the conduits of the drawing in and out system by means of 
manholes placed at an average distance apart of about one tAventy-fiftli of a mile. 
The manholes are generally of brick or cast iron. Access is had to the manloles from 
the street through a cast iron head, which is provided with double covers. 

Into the ducts thus provided insulated cables, or separate conductors, are drawn, 
from manhole to manhole, by the use of a winch, in the manner indicated in Fig. 390. 

When the cable is not very heavy it may be drawn into the duct by hand. 

Bef .re the cable can be drawn into the duct a rope has to be passed through the 
duct by a jDrocess termed " rodding." Rods, about three feet in length, with a 
screw thread and screw socket on their rtspective ends, are shoved into the duct, one rod 
after another, until the distant manhole is reached. The work of attaching the rope 
to a large cable requires considerable skill and care. The connection is generally so 
made as to put the strain chiefly on the conductors. 

In case of a defect to a cable, or ^ conductor, it is drawn out and another substi- 
stuted: hence the distinguishing name of the conduit. 



When it is desired to make exit from the underground conduit to a polo lino, or 
to a house top, a " subsidiary" duct is run from the nearest manhole to the polo or to 
the side of the building chosen; up whicli a tube, in which the cable is plaood, is 
continued, until the actual distributing point is reached, wlien the conductors are "' fan- 



526 



AMERICAN TELEGRAPHY. 



UNDERGROUND TELEGRATH CABLES. - 
FIG. 391. 



ned " out 011 the cross-arms, as indicated in the figure representing house-top iixtiLres 

in chapter on " Construction." 

The average number of conductors in a tele- 
graph underground cable, in 
large cities, is about 50 , although 
much smaller cables are also 
used. In Fig. 391 a specimen 
of an 18 conductor cable is 
shown, c is the ^.entral wire. 
M and m' are '^marking " wires 
for the separate layers, which 
are useful in identifying tlie 
conductors in testing, jointing 
and numbering, t is the tape 
as a rule, No. 16 b. w. g. and the outside diam- 
This outside diameter includes that of the 




FIG. 392. 



covering. The size of the wire used is, 
eter of its insulated covering is ^% inch, 
conductor. 

The types of cables more generally 
used by the telegrapli com])anies of 
this country, for underground service, 
are those known as the " Kerite, *' 
" Okonite," *' Safety' ' '' Standard '' 
and " Paterson." 

The insulation resistance of t h e 
*' Okonite" insulation is given as about 
2500 megohms; that of "Kerite," 
about 800 megohms ; that of the 
"Safety," about 2000 megohms, and 
that of the " Standard " and '• Patter- 
son," about 1500 megohms, each, per 
mile, all for the thickness of insulation 
just stated. 

Gutta-percha is not in extensive 
use in this country in underground 
service, owing to its low melting or 
softening point, which is about 135° 
F., a temperature which is frequently 
met with in the streets of large cities, 
at the points where boilers and subway manhole. 

furnaces encroach on the streets, in vaults and elsewhere. 

CABLE JOINTING.— After having been drawn into the ducts the conductors of the 
cables are then jointed. In Fig. 392, which represents a manhole of the Johnstone 
conduit system and in which the ducts are more clearly seen, the ends of a telegraph or 
telephone cable are shown in readiness for jointing. Care is, of course, taken co 
keep the ends viry. The manner of making the joints depends upon the nature 




UNDERGROUND CONDUITS. 



527 



covered, to ex- 



of the cable. If of fibrous material the cable will, as a rule, be lead 
elude moisture. lu that case joints are generally made by carefully connecting the 
ends of two conductors together by a twist joint, which is soldered, lightly. The joint 
is then covered with a semi-insulating tape. After all the conductors have been thus 
jointed a lead sleeve is placed over the joints. This sleeve is next soldered on to 
the lead covering and one or two holes are punctured in the sleeve. Into the sleeve, 
a hot, insulating liquid, such as paraffin, is then poured. This liquid subsequently 
hardens- Tlie holes in the sleeve are then soldered. 

If the cable be insulated with India rubber compound it is not always lead cover- 
ed when used underground for telegraph purposes. Several thicknesses of tape are, 
however, generally placed around the cable and, also, in some cases, a 2:)adding of 
jute. Joints on this type of cable are made as follows: First, about one inch of the 
insulation is removed from the ends of the conductor; the ends of the conductor are 
then "sweated" together, asniitU, split, copper sleeve being usually placed over the 
ends. When the sleeve is not used, the ends of the conductors are filed and then 
placed together' and wrapped with fine wire. No acid is used in soldering; resin 
being commonly used as a flux. After the wire has been spliced the insulation is 
then scarfed, that is, tapered oflf, for about three-quarters of an inch. A layer of 
pure rubber strip is then wrapped around the wire, spirally, back and forth, about 
three times, and each time the rubber is brought further up the scarfed insulation. 
A few layers of white, or unvulcanized, rubber strip is then wound above the pure 
rubber layers, and after that one or two layers of a pink rubber strip is put on. A 
layer or two of fibrous tape, with a rubber coating, is then placed over all. Between 
each layer of rubber strij) a small quantity of rubber solution is applied to make the 
rubber adhesive and, practically, homogeneous. If the cable should be lead covered, a 
few inches of the lead is stripped off prior to proceeding with the joint making. 
After the joints have been made a lead sleeve is then shoved over all, and " wiped " 
on to the lead covering. 

MEASURING INSULATION RESISTANCE OF JOINTS. — In Underground and submarine 
cables it is very necessary that great care should be used in making joints, inasmuch 

as they are conceded to be the weak points 
of all cables. When joints are made in 
the factory it is easier to test them than 
when made under the conditions accompany- 
ing the laying of the cables underground or 
underwater, and, except in the case of 
very important, long cables, a joint is rarely 
tested outside of the factory. 

When it is desired to test a joint for 
its insulation resistance it mav be done as 



FIG, 393. 




TESTING JOINTS. 



indicated in Fio-. 



in which 



vessel filled Avith salted water; kk is a revers- 
ing key ; B is a battery of 50 or 100 volts or more, g is a galvanometer, the ionsfaut of 
which has been ascertained in the usual way. c is the cable,having one of its ends 
connected to galvanometer, and its other end free, and insulated. The joint .v is 



528 



AMERICAN TELEGRAPHY 



immersed in the water of the vessel. The wire w is placed directly in the water. 
Tlius when the key is depressed any current flowing in the circuit must pass from 
the joint through the water to the wire w. Hence, the deflections of the needle, if 
any, obtained, furnish data from which to calculate the resistance of the joint. 

RIVER AND HARBOR CABLES. — As a rulc, but ouc conductor is used in long ocean 
cables, as, for exami3le. in the case of the Atlantic cables. Gutta-))ercha is chiefly 
used as the insulating material. The conductor of such cables is of the purest 
copper obtainable and is generally composed of 7 copper wires. Tlie strand thus 
formed is covered witli th)-ee or four separate layers of gutta-percha, and between 
each layer a compound is placed which unites the different layers into practically one 



FIG. 394. 



FIG. 395. 





covering. One object in using several layers of gutta-percha, in the construction of 
the cable, is that, in the process of covering the wire with that material, air holes are 
liable to occur. If but one layer were used it is evident that the de /elopment of an 
air-hole into a "fault" would speedily follow the immersion of the cable. By put- 
ting on the different coatings of gutta percha any air-holes that may exist in any one 
layer are rendered practically of no effect. Tarred hemp is then placed over the 

FIG. 396. 




gutta-percha, and, over the hemp, a number of twisted galvanized ii'on wires, forming 
the " armor," is finally placed. 

For crossing rivers and bays in this country, cables containing from i to 7, or 
more, conductors are employed. The insulation employed is mainly India rubber or 
gutta-percha, while, for short crossings, lead covered and armored, fibrous cables, are 



CABLE TESTING. 529 

also used. The thickness of the armor and particular construction of the cable de- 
pend upon the nature of the river or harbor bottom and the general conditions like- 
ly to be met. 

In Fig. 394 is shown a cross-section of a 7 -conductor, fibrous, lead covered cable, 
c being the conductors, i the insulating material, l the lead covering, a the galvanized 
iron armor. Fig. 395 represents the section of a 7 -conductor rubber compound or 
gutta-percha, jute padded, and armored cable; c representing the conductors,! the 
insulating material, p the padding and a the armor. In Fig. 396 is shown a 7 -con- 
ductor india-rubber compound cable intended to withstand severe strains and abra- 
sions, as where ice might be expected on river beds, etc. Each conductor is 
cushioned by a thick, jute cord, while between the conductors and the heavy armor a, 
three layers of jute packing p,p^, p^, are interposed. 

Cable Testing, Remarks Concerning, Etc. 

The arrangement of apparatus for measuring the insulation resistance of wires 
and cables has already been shown and described in Chap. VIII. 

In making such tests, if the cable is a long one, the galvanometer, as previously 
remarked, should be momentarily short circuited when the battery key is first de- 
pressed. It will be found, after the short-circuiting key has been raised, that a large 
deflection is still observable. If the insulation of the cable is perfect the deflection 
will diminish rapidly at first, and more gradually afterwards, until it reaches a 
point where for practical purposes, it may be said to be permanent, although, in real- 
ity the effect will continue indefinitely. This phenomenon, as has been stated, is 
due to electrification. 

With a given cable, in good condition and after the previous charge has been en- 
tirely dissipated by *' grounding " the cable, it will be found that at a given time of tak- 
ing the readings, the deflections will be the same with either pole of the battery to 
the cable. For instance. Assuming that it is intended to take i and 3 minute read- 
ings ; that is to say, after the key which places the battery to the cable has been 
closed for one minute, a note of the deflection is made; at the end of 3 minutes an- 
other reading is taken. If a deflection of , say, 200 is observed, after the first minute, 
and 100 after the tliird minute, with, say, the positive pole to the cable, exactly simi- 
lar deflections should be observed, after i and 3 miiuites, respectively, with the nega- 
tive pole to cable. If sucli is not the case, and if careful examination shows that the 
Tariation is not due to imperfect connections or apparatus, a defect may be looked for 
in the cable. It will generally be found in such cases that the copper pole of an in- 
creased battery applied steadily for a time to the cable will develop, or '•' break 
down " the fault. 

When, however, the deflections are eve7i the insulation resistance of the cable is 
computed from the readings taken at the first or third minute, as may be preferred; 
the one minute reading generally being specified. 

The action, or effect, of electrification varies markedly in cables of different in- 
sulating materials, being more pronounced, according to the experience of the present 
writer, in India rubber and gutta-percha cables, than in iibrous. lead- covered cables. 
It also varies in different rubber compounds. 



5 30 AMERICAN TELEGRAPHY. 

In certain types of rubber compound "insulations," of which the writer has tested 
many hundreds of miles, it was noted that, in faultless cables, the electrification pro- 
ceeded with such unvarying uniformity that, after the first reading, the defiection at 
the subsequent readings could be unfailingly predicted successfully. It was found, 
for instance, that the deflection at the third minute wonld always be one half that of 
tlie deflection at the first minute, etc. 

In taking readings it will be found advantageous to "tap" the short-circuiting 
key, momentarily, until the deflection comes within the limits of the scale, which, as 
a rule, will be within a few seconds after the battery key has been depressed. Then 
the short-circuiting key may be "clamped" down, or held down by the fingers, until 
the close of the readings. 

For insulation tests it is, in some cases, preferable to use high electromotive force, 
as it is moi-e searching, that is, the pressure 12 greater and, consequently, the tendency 
to a disruptive charge is greater and also, with a given electromotive force and re- 
sistance, the current will be greater. As the chemical action of a current is propor- 
tional to the current strength, it follows that a strong current might develop a defect 
that would remain unnoticed under a weaker current. Nevertheless, the actual insul- 
ation resistance of a material, iu the absence of the conditions necessary for electro- 
cliemical action, may be as accurately measured, with one cell, and a sufficiently sensi- 
tive galvanometer as with a battery of 100 cells. Of course the e.m.f. should not be so 
high as to break down the normal resistance of the insulating material, 

LOCATING FAULTS IX CABLES, ELECTEO-MECHANICALLY. 

The following, so to speak, " rule of thumb " electro-mechanical methods of lo- 
cating faults in cables in which the defect is not a pronounced one, such as a dead 
"ground" or " break. " have been adopted by some experienced repairers of sliort 
submarine cables in this country, in preference to the electrical methods which miglit 
be employed to locate the defect, and which methods are, in many instances, rendered 
more or less uncertain by the lack of data concerning the exact resistance and 
length of the conductors, (especially when the latter are " laid '' up spirally) and other 
information essential to satisfactory results. It should, however, be said that, in the 
hands of experts, tlie " Yarley loop, " and other methods of locating such faults, have 
been found to give quite accurate results in numerous instances of defective subma- 
rine and underground cables. 

POINT TO POINT METHOD. — Imperfectly developed defects in un armored cables in 
the factory or store-house may frequently be located by tests made from " point to 
point" of the insulation, in some such manner as the following, {See Fig. 397). 

The cable is placed in a tank T,or on a damp floor and well wetted. One end of 
the cable is connected to the terminal of a sensitive galvanometer g, the other end is 
kept well insulated; the other terminal of the galvanometer is connected to ground, via 
a battery, as shown in the figure. The galvanometer will be deflected by the current 
due to the, comparatively, low resistance of the defect. The cable is then slowly coiled 
on to insulated stand i. If the deflection of the galvanometer needle is closely watched 
it will be found that when the defective p'ortion of the cable leaves the tank there wall 
be a drop in the deflection. Much of the success of this method depends on keeping the 



LOCATING FAULTS IN CABLES. 



53 



stand I tnoroughly insulated. Care must also be observed that the "defect" does not 
get a" ground " after it is on the insulated stand, by way of the wet surface of the cable. 
Whether it has done so can be determined by occasionally drying off a few inches of 
the surface of the insulating material of the cable, between the tank and stand, as at :r. 
The insulating material may be readily dried by the judicious use of the heat from a 
spirit lamp. If the cable is juted or taped this must be removed and the insulation 
proper exposed and dried. If the defect, after one of these dryings, is found to be 
on the stand, the cable is then coiled slowly back into the tank until the defect leaves 
the stand. The vicinity of the defect is thus ascertained, and by using care and 
gradually shortening the length of cable operated on, the defect may be located to 
within a fraction of an inch. Sometimes, on inspection of the insulation, the defect 
is visible when it first leaves the tank. 

With armored cables it is not thought advisable to cut the shield in the manner 
suggested in the case of jute and therefore it would be useless to coil the cable on to 
the insulated stand with any hope of finding the defect. When faults occur on lead- 
eovered or armored cables the defect is sometimes located by running the cable over a 
" drum " and observing any change in the deflection that may be caused by the vari- 
ation of the resistance of the defect in passing on to the drum. When such an indica- 
tion is manifested the suspected spot is beaten with a wooden mallet to further de- 
velop the dpfect if it exists at that point. 

LOCATING FAULTS IN SHORT SUBAQUEOUS CABLES. — In locating faultsin subaqucous 
cables, laid across moderately narrow bays or rivers, a method called "under-running," 
which is practically similar to the la^t described, is employed. 

FI3. 397 




A "shore" end of the defective conductor of the cable is connected with a galvanom- 
eter and battery, as in Fig. 397. A flat boat, with a set of rollers or ^^"lleys on its 
deck, having been provided, a portion of the cable near one of the shores is lifted on 
the boat and placed in position on the rollers. The boat is then started across the 
bay, the cable rising out of the water on one side of the boat and falling into it on 
the other side. This, of course, eventually takes every portion of tlie cable out of 
the water, for a few seconds, and the change of position almost invariably alters the 
resistance of the defect as it passes over the boat. When this variation of tlie re- 
sistance is observed by the attendant, the boat is signaled to that effect. The boa-^ 
is then moved back and forth until the exact location of the defect is found. 



CHAPTER XXXIIL 

Construction and Maintenance of Telegraph Lines. 

AEEIAL CABLES, ETC. 

Generally speaking, it may be said that in building a telegraph or telephone line 
in this country no regular survey of the route is made. It is, however, customary, 
after the general route of the line has been selected, to prospect for the shortest and 
best route. In the performance of this duty the official engaged is e.^^ected to note 
whether the digging will be medium or rocky and to designate the height of poles 
necessary to clear the trees to be encountered at certain points, etc. 

After the route has been thus selected it is important to obtain the right of way, 
or, as it is termed elsewhere, " w^ay leave " ; in other words, permission to erect the 
line on public and private property, along the route selected. 

If the line is to follow and be constructed on the property of a friendly railroad, 
the question of right of way is quickly settled. But, if it is a " highway," or " pike " 
line, the question of right of way is one requiring much attention. 

The mode of procedure for obtaining rights of way is different in almost every 
state in this counti-y. In some states it is necessary to apply to the road supervisors for 
permission to set poles in their districts. In others, the towai selectmen, of whom 
there are generally three to five, furnish necessary authority for the purpose. It has 
happened that lines have been constructed semi-surreptitiously along country roads , 
but in the end it has often proved an expensive undertaking. 

Kigl)ts of way should be obtained, in writing, if possible, for every pole set. This 
wall fi'equently save trouble and the expense of moving the poles, as well as 
litigation expenses, after the line has been built. 

The poles and other materials are brought to the route of the line by the most 
available means. If it is a railroad " route," the poles, wire, etc., are placed on a 
truck car and thrown off at the proper intervals, as the train moves slowly along. If 
the line follows a highway the material must be brought to the nearest point by rail 
or boat and thence to the route of the line by teams. The number of poles, per mile, 
is, of course, determined in advance; 35 to 40, per mile, being the average. In some 
cases no naore than 25 poles, per mile, are used. 

POLES. — In choosing poles for an overhead telegraph line the locality of the line 
is taken into consideration. For use in cities, Norway pine is generally selected. For 
this purpose the poles should be from 50 to 80 feet long. In some special cases even 
longer, as when very high buildings are to be surmounted. Other timber used for- 
poles in this country includes cedar, chestnut and cypress. The average life of Nor- 
w^ay pine may be placed at 6 years; that of chestnut, 15 years; cypress 12 years; cedar 
10 years, according to Mr. J. A. Helvin, to whom I am much indebted for informa- 
tion on this subject. 

532 



TELEGRAPH LINE CONSTRTCTION. 533 

Th3 poles should always be well seasoned. The process of seasoning consists, 
essentially, in promoting the evaporation of the sap. In some instances this is done 
by a resort to drying rooms, but tlie best results are obtained by exposing the poles 
to a free circulation of air, in a sheltered place, until tlie sap has evaporate . 

Before seasoning the poles should be peeled, and the knots should be shaved smooth. 

Poles are said to be more durable if peeled when the sap is down, but are more 
readily peeled when the sap is up. The first place at which, as a rule, poles begin to 
decay is close to the ground, at the point termed the " wind and water " hue. To 
prevent, as far as possible the " wind and water" effect, it is sometimes customary in 
this country to coat the butt end of the pole, that is, the end which goes in the earth, 
witli pitch, to a distance of 6 feet from the end. 

The length and thickness of the poles required will, of course, vary with the 
number of wires to be carried, and, also, with the conditions existing along the route 
of the line. For instance, if there is much shubbery along the route, for a line of, 
say, 22 wires, an average length of 30 feet will suffice. This will allow of " setting " 
the poles to the depth of 5 feet in the ground, and yet leave considerable space be- 
tween the lowest wires and shrubbery. For a line of 40 wires the poles should average 
40 feet and should be set 5 to si feet in the ground. If, in this case, there hre trees 
along the route, it is expected that the wires will pass under the foliage, where thickest. 
For a line of from 40 to 200 wires, (there is a telephone line qf over 300 wires iu 
present existence in New York City) the poles should average 73 to 80 feet in length, 
and, depending on the nature of the ground, should be set 7 to 9 feet therein. In this 
latter case it is assumed that the wires pass over the foliage of trees. 

In all cases where wooden poles are to carry " cross-arms '' {See "cross-arms") 
they should not be less than 7 inches in diameter at the top end. 

IRON POLES. — Iron poles are used in some places in this country for telegraph 
purposes, but not very extensively. They are used chiefly by the United States gov- 
ernment, more especially in the far west, and along the coast, in the Signal service; 
being considered preferable, in that they withstand, in the one case, the prairie or for- 
est fires, and, in the other, at least to a greater extent than wooden poles, the heavy 
surfs and storms that prevail. In " commercial " telegraphy, and in telephony, iron 
poles are rarely employed ; the fact that the breaking of an insulator or the slip]:)ing 
of a pin will cause an immediate ground, should the wire touch the pole or cross-arni, 
militating against their use. 

ERECTION OF POLES. — The principal tools used in digging the hole for the pole 
and in handling and raising it into position, are the spoon shovel ard long shovel, 
( Figs. 398, 398^ ) tamping bar, Fig. 399 ; round-face tamping bar ; the 
*' paddle," Fig. 400; "deadman,'' Fig. 401; cant hook. Fig. 402. A post-auger, Fig. 
403, is sometimes used to bore holes when the nature of the ground will permit; that 
is, in sandy or clayey soil, but, in general, the " long " and " spoon " shovels, and 
pikes, are employed in hole-digging, the latter to loosen the earth. 

The depth of the hole varies with the length of pole and nature of the ground. 
For 30-feet poles the hole should be 5 feet deep in soil, and, at least. 4 foot in solid 
rock; for longer poles the holes should be proportionately deeper. 

The hole having been made , the "paddle" (shaped as indicated in tiguroHs 



534 



AMERICAN TELEGRAPHY. 



placed in it, on one side, to serve as a rest for the "foot," or butt, of the pole. By 
tlie aid of cant-hooks the pole is rolled with its butt end over the hole. It is tlien 
raised slightly and its butt slipped into the hole where it -rests against the paddle, 



FIG. 3,-8. 



FIG. 398 a 



FIG. 399. 



FIG. 400. 



SPOON SHOVEL. 



LONG SHOVEL. 



TAMPING BAR. 



THE PADDLE. 



which prevents crumbling down of the earth from the side of the hole. The pole is 
then raised higher, and the " deadman, " or " butt-prop," as it is also termed, is put 
under it. This supports the pole until a new hold is obtained, whereby the pole is 
raised still hig'.^ier, which accomplished, the prop is moved nearer to tha. butt, '/rhe 



TELEGRAPH LINE CONSTRUCTION. 



535 



'' deadman " consists of a short wooden bar on one end of which are two iron tines, 
U-shaped, with a small sharp spike between them. The tines partially embrace the 
pole, while tlie pike prevents slipping.) Sharp pikes at the end of long poles, Fig., 
404, are then thrust into the upper part of the pole, on both lower sides of it, by 



FIG. 401. 



FIG. 402, 



FIG. 403. 





DEAD-MAN.' 



CANT HOOK. 



POST AUGER. 



means of which it is raised to a vertical position, when it slips down into the hole. 
The cant-hook is again used to turn the pole in the hole, so that the '• gains," or 
notches, which have been cut in its side for the cross-arms, will be at right angles to 
the wires, as they run. The hole is then carefully tilled, the soil, stones, etc., being 
tam|>ed, or beaten down, by the " tamping" bars, in process of tilling. The work oi 
tamping should be well performed, as, upon that much of the future stability of die 
poles depends. In places where the ground is soft, a foot-])late, somewhat similar to 
that shown in Fig. 405, is placed under the butt of the pole to increase the stability 
of its foundation. 



536 



AxMERICAN TELEGRAPHY. 



Poles placed on curves or corners should be set sloping, to an extent depending 
on the sharpness of the curve, and against the pull of -the wires. Where the line un- 
der construction is to cross an existing line the poles should be of sufficient height to 
carry the lowest wires well over those of the line crossed ; or, if that course should 
prove to be impracticable, owing to the height of the other line, a guard wire should 
be placed on the top of the new line to ward off lower wires of the existing line. 

GUYING. — A very necessary part of telegraph line construction is the "guying" 
of the poles. Guying consists in attaching to the pole, at a desired point a wire, or 

FIG. 404. 



FIG, 405. 



str^ind of wires, termed the guy wire (which, at its further end, is suitably fastened, or 
" anchored ") for the purpose of strengthening the pole in its position. Guying is es- 
pecially necessary in the case of "heavy " lines, that is, those carrying a large num- 
ber of cross-arms and wires. Such lines should be well guyed, both "head" and *'side," 
before the wires are strung. A "double-head" guy is made by fastening a heavy guy 
wire to the top of a pole, or at about the fourth cross-arm from the top, and running 
the wire to the next pole, in either direction, and then fastening it to the latter pole, 
say, ten or twelve feet from the ground; and then running, from the top of the latter 
pole, to near the base of the former, a similar, strong wire. This forms a horizontal 
X between the two poles. The double head guy should be placed every fourth 
or sixth span, where the line is exposed to heavy winds. 

A " side " guy/ is formed by attaching a " guy " wire, of suitable dimensions, to 

the top of a pole, as in the case of the "head" 
guy, and thence running it to an adja- 
cent tree, to a house top, or to a guy "stub," 
placed some distance from the side of 
the pole. A " guy stub " consists of a stub 
of a pole set in the earth at an angle away 
from the pole to be guyed. " Side " guys 
should be put on each side of the pole, lat- 
erally, so that the wind may not have an 
advantage either way. 

An " anchor " guy is constructed in the 
following way : The guy wire is fastened 
arms, under the fourth 
arm. A hole is then dug in the earth, 5 or 6 feet deep, at a distance of about 10 or 
15 feet from the pole An " anchor," consisting of a heavy stone, or even green wood, 
is then placed in the hole, first having attached to it the other end of the guy wire. 
The hole is then filled up with earth which is well tamped down. The anchor guy is 
used where a " stub " can not be employed or where a tree is not available. 

No. 8 or ISTo. 6 b.w.g. galvanized iron wire, single or formed into a strand by twist- 
ing together as many wires as may be necessary, is generally used as guy wire in 
telegraph construction work. 




" FOOT" PLATE. 

under the bottom cross-arm, or, if there are more than 4 



TELEGRAPH LINES. 



53 7 



It is sometimes necessary to span rivers or ravines of moderate width. In such 
cases tlie poles at the banks require extra guying and " strutting." ' Struts" con- 
sist of poles or " stubs," bearing against the regular pole in a direction contrary to 
the strain. 

When a span would exceed, say, 300 feet, at a river crossing it will be advis- 
able and, in the end, economical, to use a subaqueous cable. There are, however, spans 
of from 200 to 800 feet of iron, and of hard-drawn copper, wire in existence in this 
country to-day which were erected over 8 years ago. Probably one of the long- 
est spans in this country was one near Trenton, N. J. This span was about 1 700 feet 
in length. It w^as made up of a No. 12 steel wire and a No. 14 hard-drawn copper 
wire. 

POLE LIGHTNING ARRESTERS. — By somc Superintendents it is deemed desirable to 
equip a certain number of poles per mile, with lightning rods. This rod is formed of 
a length of iron wire twisted repeatedly arour d the butt of ^^q^ ^06. fig. 406 a. 
the pole and thence continued up the pole to the top, and 6 
inches beyond. 

BRACKETS, PINS, CROSS-ARMS. — The wircs are suspended 
on the poles in two ways : Namely, by means of brackets 
and cross-arms. 

Brackets (Fig. 406) are simply pieces of wood sloping on 
one side and straight on the other, with a screw thread on the 
upper end to carry the insulator. 

Brackets are not often used when more than two wires 
are to be strung on the poles. The bracket is nailed to the 
pole with the straight side out, to leave a space between 
the pole and insulator. Where a " bracket " line is to cany 
two wires, one bracket should be put on one side of the pole 
and the other on the opposite side, one about 15 inches above 
the other, to prevent the wires from crossing, in the event of 
one of the brackets breaking off and falling. Furthei*, if 
it is necessery to put more than one bracket on one side of a 
pole, the wire should be '' tied " on the in side of the bracket, 
so that, if the insulator be broken or pulled off, the wire will 
rest on the bracket until the insulator is replaced. bracket. pin. 

The " cross-arm " is composed of an oblong piece of wood of varying length and 
thickness, according to the weight it may have to support, placed cross wise on the 
poles. On the cross-arms are placed '^ pins," Fig. 406^, for the insulators. In Fig. 
407 is shown a pole p, with cross-arms a, pins p', brackets b with insulators /,/', 
and wires in position. Notches, or ^' gains," are made in a side of the pole to afford 




a flat surface for the cross-arms The gains should not be less than two inches in 
depth and should be cut to hold the cross-arm snugly. Tlie top gain shouki be about 
eight inches from the top of pole; the other gains should be twenty-four inches apart. 
The cross-arms are placed in the gains after the poles are in position, and are fastened 
to the poles by means of spikes of desired size, similar to those shown in Fig. 408, 



OJ* 



AMERICAN TELEGRAPHY. 



known as Fetter drive screws. The pins for the support of the insuhitors are placed 

on the cross-arms in advance. Locust pins are the most durable and most capable of 

withstanding heavy strains. Tlie cross-arms 
and pins should be painted before their 
erection on the poles. In some cases 
they are simply dipped in paint, but this 
has not been found a durable method of ap- 
plying the preservative. Specifications gen- 
erally state the exact manner in which 
these details are to be executed. 

The number of wires to be strung on the 
poles having b e e n determined in ad- 
vance the desired size and the number of 
cross-arms is arranged for. P'or telegraph 
purposes 2, 4, or 6-pin cross-arms are most 
frequently used, as arms of 'those sizes 
allow a larger space between the wires. 
In putting up cross-arms on lines of all 
kinds the arms should be reversed on every 
other pole; that is, the 'gains'' should be 
on one side of one pole, and on the other 
side of the next pole, as one looks along 
the line. This tends to keep a uniform 
strain on the poles. 

Insulators. — Some of the essentials of an 
insulator, for aerial purposes, are that 
it shall have high electrical resistance, shall 
possess strength, permit a good hold upon 
the Avire, shed rain freely, have no dark 

recesses for the accommodation of insects, and be reasonably cheap. 

As these requirements are found but rarely in any one substance it is evident 

that the available materials are limited. For instance, iron would possess strength, 




FIG. 408. 



^'•iiiiiiiiiiiiifiiiiiiP 



FETTER DRIVE SCREW. 



but it is not an insulator, and glass possesses non-conducting qualities but is more or 
less brittle. A combination of both might possess strength and high insulation but 
would be opaque. 

In Europe, porcelain and earthenware insulators are very extensively employed 
and are highlv esteemed. They have also been used in America, but at the pres- 



TELEGRAPH LINES. 



539 



eut time and for many years past a glass insulator is and has been praetieally tlie 
only one employed in the telegraph, and, it may be added, the telephone service. 

It is claimed for porcelain and earthenware insulators of the higlier grades that, 
besides possessing, normally, higher electrical resistance than glass insulators, in moist 
and damp weather, they do not tio. 409. 

accumulate, on t h e i r surfaces, 
moisture, to the same extent as 
glass and, therefore, that they are 
n much superior insulator than 
glass at such times. On the other 
hand, it has been observed, in this 
country, that vermin are more apt 
to build in the recesses of the 
porcelain insulators than in the 
glass, (presurnably owing to the 
greater opacity of the former), 
and, also, that, apparently, soot 
adheres more firmly to the former 
tlian to the latter, both of which^ 
it is well known, tend to reduce 
tlie insulation, especially in wet 
weather. Doubtless, however, the 
greater cost of porcelain and 
eaithenware, especially the for- 
mer, as compared with glass, has 
been an important factor in pre- 
venting a more general use of those 
materiak as insulators, in this 
country. glass insulator. 

Experience lias, however, also shown, in this country, that, given a wire free 
from foliage, kite tails, etc., the occasions are rare when a line well insulated with glass 
will not work fairly successfully in ordinary wet weather. ^ 

On repeated occasions the writer has found that certain long overhead 
circuits which, within city limits, were practically useless, owing to low insulation, 
when tested outside of those limits were found to be in o-ood workino- order. 




Tlie styles of the " American " glass insulator vary in numerous ways, namel 



v: 



as to its shape, the location and depth of the groove for the wire, the depth of the 
hole for the pin. the number and depth of the screw-threads within the insulator for 
tiie pill, etc., but its general appearance will be seen in Fig's. 409, 410. The latter is 
known as the "B and O" insulator; its weight is about 22 ounces. 

A smaller insulator of the same general form, termed a " pony " insulator, Ficr. 
411, is much used for No. 12 b. w. g. hard-drawn copper wire. 

The location and depth of the wire groove requires consideration. If it is too 
shallow, the "tie" wire slips out easily. If too deep, the strain of the tie wire is apt to 
crunch the glass, thereby inii)aring the insulation; in fact, introducino- a source of 



40 



AMERICAN TELEGRAPHY. 



defective insulation, often very difficult to discover. The lower tlie groove on tlie 
insulator the less is the strain on the supporting pin, but at that point the glass is 
thinnest. 

The bell shaped form gives a good water shed and tends to throw the "drip'= away 
from the pin. 

In order, further to keep the pin dry, some insulators are made with a double 



FIG. 410. 



FIG. 411. 




B. AND O. INSULATOR. 



PONY INSULATOR. 



" petticoat," as seen in Fig. 412, in which a section of the lower part of the in- 
sulator is removed to show the double petticoat. This insulator is known as the 
W. IT. " double petticoat " insulator. In Fig. 413 is shown a form of insulator de- 
signed to still further increase the insulation of the insulator by decreasing its surface 
where dt would come in contact with the line wire and " tie " wire. It also 
facilitates the cutting of the tie wire ; that is, the piece of wire which ties the line wire 
to the insulator. Economy is also aimed at by reducing the weight of the glass without 
materially decreasing its strength. The manner in which both of these results are 
designed to be effected will be obvious on examining the illustration. In Fig. 410 
the tie wire is passed around the upper groove. The bulge above the upper groove 



WIRE STRINGING. 



54^ 



13 designed to throw off the water from the wire and pin. The object sought m run- 
ning the pin so far up in the bell is that, in case of the breaking of the glass, the tie 

FIG. 41 J. 



FIG. 412. 




W. U. INSULATOR. 

wire may still be held by the pin upon the cross arm. 

FIG, 414, 




RUBBER INSULATOR. 

A rubber insulator in which an iron hook is inserted, as snown in Ficr. 4x4, is usett 



542 



AMERICAN TELEGRAPHY. 



extensively on the underside of cross-arms, in cities, especially on house-top fixtures. 
TEEE INSULATOR. — When from any cause whatever it is found impracticable to 
pass beneath or to surmount a grove of trees so as to avoid the foliage, it will be 
necessary to use insulated wire through that portion of the route. 

FTG. 415. 




In isolated cases, where the owner will not permit the placing of insulators on 
trees to ward off the wires from the trunk or boughs, a tube of vulcanized rubber 
placed over the wire has been found of much utility. 

An insulator designed for attachment to trees is shown in Fig. 415. It may be 
fixed at any desired angle. The manner of its application will be obvious by a glance 
at the drawino'. 



Wire Steinging. 

Although hard-drawn copper wire has been found to give very satisfactory ser- 
vice as an aerial telegraph wire, it is still thought advisable by some telegraph engi- 
neers, in tlie construction of a line of that wire, to strengthen it by the use of one or 
more iron wires. 

As to tlie manner of placing the iron wires to obtain best results, opinions 
differ. When but one iron wire is used, however, a No. 6 or 8 b.w.g. iron wire is 
generally placed on a pin on the top of the pole. When more iron wires are used, it 
is, by some, considered advantageous to erect, first, a 4-pin cross-arm, and on this to 
string a No. 6 p..w.g. iron wire, each side of the pole, stringing the copper wires on 
the adjacent pins. If the line is a heavy one this process may be repeated, say, 
every third or fourth cross-arm. 

Assuming the copper wires to be No. 14 b.w g., No. 6 iron wire could be used, 
in wire "patching," interchangeably with the copper wire, the electrical resistance of 
each being nearly alike, namely, about 8.5 ohms. 

The poles, cross-arms, etc., having been placed in position and the poles thorough- 
ly guyed, the men engaged in stringing the wire follow up, closely. This force con- 



WIRE STRINGING. 



543 



FIG. 416, 



slsts of '' cOimbors," that is, the men wlio, by the aid of linemen's "spurs," climb 
the poles to attach the wire to the insulators; and the men who " pull " the wire 

taut, for the climbers. The 
wire, put up in coils of the 
length that may be specified, 
is generally carried on a barrow- 
reel, Fig. 416. Grjat care 
should be taken to prevent the 
wire from kinking, or from be- 
ing bruised. When kinks occur 
they should be cut out and the 
wire jointed. This is especially 

necessary in the case of hard drawn copper wire. 

In stringing the wire it is first pulled loosely over the desired cross-arm for a 

number of poles. The " pullers " then haul on the wire until it is taut; a " block and 




WIRE BARROW. 



FIG. 417. 




' COME ALONG. 



fall " may be used to pull up iron wire, but copper wire should be drawn up, level 
with the iron wire, "hand tight," as construction men term it; that is, without the 
use of vices or " come-a longs." 



FIG. 418. 




COME-ALONGS.— A " comealong" is shown in Fig. 417. It consists of an eccentric 
clamp c, supplied with a ring and strap, as shown. The wire is placed in the clamp 
and the hneman gets a purchase for one end of his strap on the pole. He pulls on 
the loose end which causes the clamp to tighten on the wire. As the wire comes in 
the buckle secures the strap in the well-known way. 

Another form of wire "grip" is shown in Fig.*4i8. It has the advantaoe that a 



544 



AMERICAN TELEGRAPHY. 



grip on the wire can be obtained with the use of but one hand. The operation is 
2>imple; the wire w is placed between the cam c and the flange r. The strap is at- 
t iched at s and the pull on the strap tightens the hold of the cam on the wire. The 
wire is released by depressing the lever l, which raises the cam. 

Wiien a wire is drawn i\\) to the tightness desired it is then fastened to the 
iiisulalor. 

TYING W'lRE TO INSULATORS. — In tying irou wii'c to the insulator the line wire is 



FIG. 419 




IKON WIRK 



FIG. 410 a. 



placed in the groove of the 
insulator. The tie wire, a 
piece of iron abouc 16 inches 
in length, is wound around 
the line wire close to the 
glass. The other end of the 
wire is passed around the 
insulator and back to and al- 
so twisted around the line 
wire. The pull on the wire 
is such as to give the line 
wire a bend at the insulator 

which prevents slipping. 

This tie, as seen from above the insulator /, is shown in Fig. 419; a section of 

the insulator being removed for clearness. 

In tying co[)})er wire to the insulator, soft or annealed copper is used. 
Owing to the sensitiveness of hard - 

drawTi copper wire to scratches or 

kinks it has been found desirable to 

depart from the method usual in tying 

iron wTre to the iusnlator. Instead^ 

the tie wire is first wound around the 

groove in the insulator and is then 

given a twist around itself, with the 

ends left parallel with the line wire; 

the latter is then placed in the 

groove in the insulator, when the 

ends of the tie wire are w^ound around 

the line wire a number of times, spi- 
rally; thus giving it a snug, but 

not rigid, resting place, in which it is, at the same time, free to move longitudinally. 

This "tie " is shown in Fig. 419^. 

SAG. — As regards the amount of " sag " to be allowed between poles, (a feature 

of line construction which is considered of great importance in other countries) it may 

be said that, in much of the recent construction w^ork in this country, the " sag " 

has been virtually dispensed with, both in the case of iron and hard-drawn copper 

the wire being drawn up virtually level with its cross-arms. This is in cases 

where the poles are comparatively numerous to the mile, say, 40; thus making 




HELVIX TIE. 



wm^ 



WIRE STRINGING. 545 

a stretch between poles of but 130 feet. It has been found that the percentage of 
" breaks " in the case of tightly strung wire has been no greater than in the case of 
wire erected with a "specified" sag. Further, the after work of taking up "slack," 
due to expansion, is rendered almost unnecessary in the case cf " tightly '' strung wire. 

Where strict regard is paid to a definite amount of sag, the strain on the wire, 
in pulling it " tight," is limited to one-third of the "breaking strain" of the wire. 
Tims, for instance, assuming the breaking strain of No. 6 b.w\g. iron wire, to be 
2100 lbs, a strain greater than 700 lbs. would not be permissible and, inasmuch as 
the strain increases the tighter the wire is drawn, it is obvious that, with a given span 
of wire, if the maximum tension stated is adhered to, a considerable " dip " will be 
noticeable. The dip in the case of the wire cited would be about two feet in a span 
of 300 feet. 

JOINTS ON AEKiAL WIRES. — As the woi'k of Stringing the wire progresses, the 
jointing of the ends of the coils, etc., becomes necessary. 

In the case of iron wire, the joint is made by bringing together the two ends of the 
wire to be joined, and causing them to overlap each other, 6 to 8 inches. One end i& 
then wound around the otlier wire 

spirally, several times, which op- fig. 420. 

eration is next repeated with the 
other end of tlie wire; this making 

a jointure sucii as that seen in ^99BO^ ^^^^^^^^^MSfU^SIMt 

Fig. 420. Tliis joint is then sold- '^yw^^^s*'^^ 

ered; soldering tools being carried ^^on wire joint. 

for that purpose. 

With .copper wire the joints are made differently, and it is necess^/y to exercise 
much greater care than in the case of the iron wire. 

JOINT SLEEVES. — In making a joint on hard-drawn copper wire a "sleeve" h 
almost invariably used. 

At one time a sleeve, known as the "Helvin,"was extensively employed, and 
hundreds of them are in use to-day. It consists of a brass cylinder, througli whiclj 

Irwo chambers are run, lengthwise. These chambers are 

FIG. 421. of suflncient size to admit the wire. One end 01 the wire 

is run into and through one of the chambers; the end ot 

the other wire through the other chamber, from the op])(j 

site end of the sleeve. The end of each wire is then 

wrapped 3 or 4 times around its adjacent wire, close uj) lo 

the sleeve, and soldered at the ends of the chambers ; the object of which is to previMit 

corrosion, etc., by excluding moisture from the chambers. 

A sleeve, now much used in hard-drawn copper wire jointing, is knctVii as th- 
Mclntyre sleeve. It is practically similar to the Helvin sleeve, having two chambei 
also, but, as a rule, no solder is used in connection with it, and the ends of the wi/ 
are not twisted ; instead, the sleeve itself is twisted; one lineman holding one end * 
the sleeve with his pliers, while another lineman twists the sleeve several times, 
sleeve, before and after twisting, is shown in Figs. 421, 421^?. This joint h;- 




546 



AMERICAN TELEGRAPHY. 



advantage that it can be quickly made, and it gives satisfactory results. Holes an 
sometimes cut in the side of this sleeve, into which solder may be run if desired. 



FIG. 42' 



MCINTYRE SLEEVE JOINT. 

t PLIERS. — Since the general introduction of electric lighting, the use of pliers, with 
insulated handles, in any kind of construction or repair work, is advocated as a pre- 
caution against accidents. In one style of insulated pliers, thick rubber bands are 
wound spirally around the handles. Another style is illustrated in Fig. 422. In this 
the insulation, /,/, is shaped to conform to the handle, and drawn over it. 

FIG. 422. 




" anti-hum" device. — In many places it is necessary, in order to retain possession 
of right of way, to obviate the humming noise due to the vibration of tlie wires. This 
can be accomplished by the use of a device known as the '• anti-hum," which is shown 
in Fig. 423. 



FIG. 423. 




A is a galvanized iron shackle, inserted directly in the line wire, near the pole, and 
provided with a washer, or cushion, of rubber, or other suitable material, to take up the 
vibrations. 

As this would break the circuit as well as the vibrations, a piece of wire, w, termed 
a "bridle" or "jumper," is passed loosely around the " anti-hum," in the manner 
shown, and is soldered to the wire on each side of a. 

CITY coNSTRUCTiox WOKK. — The general method of constructing a telegraph line 
in a city does not vary much from that in the country, except that, as a rule, the work. 



WIRE TESTING. 



547 



owincto the crowded condition of the streets, the presence of paved sidewalks, etc., is 
much more difficult. The work is also rendered more onerous by the more frequent 
objections of owners of property to the presence of poles in front of their premises. 
Tliese objections may be diminished if the sites chosen for the poles are located on the 
house, or lot, lines. 

FIG. 4?4. 




HOUSE TOP FIXTURE, "DOUBLE," WITH CABLE BOX, ETC. 

HOUSE-TOP FIXTURES. — In the larger cities a great many wires are supported on 
what are known as " roof " or " house-top " fixtures. There are "double" and "single'' 
bouse-to]) fixtures. They are composed of stout scantling, and have perpendicular 
frames Avith lateral cross-pieces, on which the pins and insulators required are supported. 
These fixtures, in some instances, carry as many as 150 wires. A standard form of a 
"double " house-top "fixture " is shown in Fig. 424. The uprights are propped, and 
frequently guyed, in every direction, to withstand strains due to high winds, etc. The 
privilege of placing tliese fixtures on roofs must first be obtained, and the rental for 
this privilege ranges from $1 to $500 or more, per annum, per fixture. This does not 
include the expense of keeping the roof in order, which devolves on the company own- 
ing the fixture. Owing to the expense attendant upon the maintenance of house-top 
lines, added to that of ordinary maintenance, and of renewals necessitated by 
severe sleet storms, etc., the telegraph and telephone companies in several of the largest 



548 AMERICAN TELEGRAPHY. 

cities of tliis countr}^ have voluntarily resorted to the extensive use of underground 
conduits, but there, of course, still remain points at wliicli the house-top fixtures are 
required in connection with the underground service.* In this case the cables from the 
underground conduits are brought to the roof in pipes or enclosed boxes, and led up to a 
" cable box" on the fixture, whence they are distributed to the cross-pieces, or arms, of 
the fixture, also as indicated in Fig. 424, in which figure the doors of the box are ar- 
ranged to show the general disposition of the wires within it. Each conductor is pro- 
vided with a lightning arrester within the box, as outlined. 



After Construction. 

The strain due to contraction of the wire, caused by decreased temperature, finds 
the weak spots in the wire, and the number of breaks due to this cause is sometimes ex- 
cessive. These breaks, it has been observed, are more noticeable along railroad 
lines than along pike lines, which may be owing to the fact that, in the former 
case, the position of each pole being taken at a certain distance, laterally, from the 
rails, the poles are in much better alignment than in the case of the highway line. In 
the case of highway lines, in the absence of surveyor's stakes, and, although care 
is exercised to erect the poles in strict alignment, they are found to be in a more or less 
zig-zag line. The result, apparently, being that, in the case of the railroad line, there 
is nothing to give way and the faulty wires break; whereas, in the case of highway 
lines, the contraction of the wires brings the tops of the poles in alignment, by which 
action the strain is relieved. 

Experience has shown that, at least, as high a percentage of breaks, due to sudden 
frosts, occurs in the case of iron as in copper wires. 

The writer remembers the interest with which, by all concerned, the first cold 
" snap " was awaited, along the route of the West Shore Railroad, after the completion, 
in the fall of 1884, of the first mixed iron and hard-drawn copper wire line of the 
Baltimore and Ohio Telegraph Co., fiom Xew York to Buffalo. This line was 
a new departure in, at least, two respects. It was the first instance of the extensive use 
of hard-drawn copper wire for aerial telegraph pm'poses in this country ; and the wires 
had been adAdsedly strung without any perceptible sag. The temperature, during one 
night, fell to 30° below zero tliroughout the Mohawk valley, and the breaks were quite 
numerous, but the record showed that, mile for mile, the breaks in the iron wire ex- 
ceeded those in the copper. However, the number of breaks was sufiicient to cause 
misgivings, and orders were issued to put some '• slack" in the wires at different points, 
but before much could be done in this direction, another equally cold snap followed, 
when it was found that the breaks were almost nil, showing that the excessive number 
of breaks in the first instance was due to flaws, kinks and other injuries, occasioned by 
the lack of proper handling and jointing on the part of the linemen, who were, of 
course, at the time, untrained in the stringing of hard-drawn copper wire. Similar 
favorable results were afterwards obtained in other sections of the country, and, as 
already intimated, a wide-spread use of hard-drawn copper for aerial telegraph wke 
purposes, followed. 

* "Roof fixtures have still further been dispensed with by the device of running the insulated wires from house to house 
in cellars and along the walls of houses in a block. This plan has been largely adopted in New York City. 



AFTER CONSTRUCTION. 



549 



MAINTENANCE OF LINES.— So mucli depends upon the maintenance of a telegraph 
line in good condition that it would almost seem super- fig. 425. 

fluous to call attention to the necessity for maintaining 
it in that condition. But it is a well known fact that there 
is no expense quite so begrudgingly incurred by some 
Telegraph directors as that for repairs to their lines. 

Shrubbery, if not cut down, will grow up into the 
wires , trees if not trimmed will grow up through them ; 
insulators will be broken and will slip off the pin ; pins will 
rot and break ; cross-arms will go awry, and poles will 
lean, in the course of time. All of these details, and many 
others, require constant supervision, and if not attended to 
the result will be shown in deteriorated service. 

Whenever permission can be obtained it is always 
best to cut down trees out of the way of the wires, 
once for all; and along railroad lines this is nearly always 
feasible But, of course, it is not, elsewhere. The next 
best thing is to obtain the consent of the property own- 
ers to trim the trees. For this purpose a "tree trimmer" is 
very usefttl, and its employment dispenses with the need 
of a step ladder to reach the boughs and limbs of trees. 
Such a tree trimmer, provided with a saw and knife, is 
shown in Fig. 425. These tools are attached by a suitable 
socket to a long pole. The method of using the saw is 
clear. It is used for cuttiug off large limbs of trees. The 
knife is operated by means of a stiff wire, extending from 
the upper end of lever l to the lower end of the pole, the 
wire being guided by screw eyes as shown. The lower end 
of the wire is furnished with a handle. The bough to be 
cut is placed in the cavity between e,c, and the wire is 
pulled upon. This brings the sharp edge of the knife- 
edged eccentric against the bough and forces it, at the 
same time, against the fixed cutting edge e. The saw may 
be readily removed by unscrewing the screws s s". 

Great care should be exercised by linemen not to disfigure trees abutting private 
property. The ruthless manner in which such trees have, in the past, been disfigured, 
has perhaps done more to incur the opposition that now exists to the presence of 
overhead telegraph lines along country roads, than any other cause. 

LINE EEPAiRiNG, ETC. — To facilitate repairs to lines, in well regulated companies 
linemen are stationed at intervals along the route. It is the duty of these men to 
patrol theii- sections for the purpose of replacing insulators; renewing pins; straighten- 
ing cross-arms; guying poles, etc. In case of line trouble occuring, such as breaks in 
the wire; crosses between wires, etc.; the chief operator, after locating the trouble be- 
tween two stations, starts the linemen from each end of a section with orders to proceed 
until they meet each other, or until they find the trouble. When, as already noted, 




TREE TRIMMER. 



550 



AMERICAN TELEGRAPHY. 



(5.:^ Locating Faults on TelegTajih Wires, Chap. VIII, page 135) the line follows 
a railroad, the linemen generally have permission to board a train, from which 
they keep a sliarp look-out for the trouble. If they descry it, and are not permitted 
to stop the train between stations, a railroad velocipede is generally brought into ser- 
vice, from the next station. This macliine, or vehicle, is constructed with three wheels, 
tvfo of wliicli, of similar size, run on one rail; the third, a smaller wheel, on the otlier 
rail. The two larger wheels are connected like the wheels of a bicycle. The third 
wheel has an axle which extends across the track to the truck of the larger wheels. 
The axle and smaller wheel are removable from the larger. The machine is propelled 
by ].>eda's. like an ordinary road velocipede. Sufficient room is provided for a lineman's 
necessarv working tools and su})plies, in a receptacle under the seat. One man can 
readilv lift this vehicle on and oft" the track out of the wa}' of trains, and by its aid a 
fault is much more rapidly reached than otherwise. 

On highway lines a horse and wagon are essential to speedy repairs. 

TROUBLE HUNTING. 

The most troublesome faults to find are often those Avhich are of but short dura- 
tion; as, for instance, a swinging cross, caused by the wind blowing two wires 
together momentarily. 

Other soui'ces of obscure trouble are those which occur only under certain condi- 
tions, as, for example, when a switch, or semaphore arm, or street gate, touches a wire, 
at intervals, and may be out of touching distance when the lineman passes. Many such 
causes of trouble are on record. 

A rather ])eculiar case of obscure trouble which came to the writer's notice was 
occasioned in the following manner : The 0|)erator in a way office, whose duty it was 
to perform certain wire service each Sunday, was given the key of the outer door of 
the building, to afford him access to his office. He carried the key with him and placed 
it, for safe-keeping, on the top of the switch board. A short while after his arrival the 
chief office of tlie Division called liim for a test of certain wires which were crossed. 
The trouble was located between the way office in question and a more distant office. 
The way office received orders to "clear" the trouble. He engaged a "team" to 
traverse the line l)ut found no trouble, and so reported on liis return, and a test dis- 
closed that the wires were clear. This same proceeding Avas repeated twice before it 
dawned on the operator that the cross was occasioned by the presence of the key on 
the top of the switch-board. 



Aerial Cables; Methods of Suspending, Etc. 

It frequently happens that it is more convenient to suspend a cable, containing a 
number of conductors, on poles than to string the same number of conductors separ- 
ately on the cross-arms. In some cases it is imperative to employ cables in this way. 
For example, the writer has knowledge of an instance in New York city where the 



AERIAL CABLES. 



551 



FIG, 426. 



only means of making connection from one office to another, was by tlie erection of 
three fifty-conductor cables, each 8,000 feet in length, upon poles which would not 
nave accommodated 10 wires strung in the usual way. Again, there are hundreds of 
instances in large cities where cables are suspended for distances varying from 50 
yards to 8 and 10 miles, as m the case of those under the elevated railroads in New 
York and Brooklyn. 

Generally speaking, the insulation of aerial cables is some rubber compound sur- 
rounded with jute and tape. Light armored cables and lead covered cables are some- 
times used for aerial purposes, but not frequently. In the case of some lead covered 
cables suspended under the elevated railroad in New York city a singular effect upon 
the lead covering was noticed after 6 or 8 months use, namely: minnte crevices 
appeared throughout the length of the cable, to the extent that the insula- 
tion, wdiich depended upon the lead covering for protection from moisture, was 
rendered defective. Tlie cracks in the lead were probably occasioned by the mechani- 
cal vibration of the elevated structure. 

The first act in erecting aerial cables gen- 
erally consists in placing in position, between 
the supporting poles or other structure, a 
*' guard" wire, which usually consists of one 
iron wire, or several iron wires stranded, 
securely fastened at the supporting points. 
This having been arranged, the cable is then 
raised, and is j^assed through a suitable pulley, 
near the guard wire. If it is a long cable, 
pulleys are placed along the proposed route at 
proper intervals, say at every other pole, if poles 
are tlie supports. TJie cable is then, by means 
of a rope attached to one end, hauled through 
the pulleys to any designated point. When 
thus drawn there is always more or less sag in 
the cable. The next operation consists in 
*'hitcliiijg-' the cable up to the guard wire. 
This is done in several ways ; one of which is 
to provide a second wire, under the guard 
wire, on which a lineman walks, and from 
whidi he proceeds to tie the cable up to the 
guard wire, by marline, at evt^ry few feet. 
As he does so the slack is taken up by other 
linemen. 




AERIAL CABLE HANGER. 



Sometimes 



metal clamp or hook, Fig. 426, is used, by which to suspend the 



cable from the guard wire. This -hanger" is, however, mostiv emploved for 
suspending cables irom an easily accessible structure, in which case the guard wire niav 
be dispensed with, the clamps being attached directlv to the structure. In otheV 
cases t.ie cpble to be suspended is tied to the guard wire wliile both are on the o-round. 
after whicV-. noth are raised together, to the suj)ports. 



552 



AMERICAN TELEGRAPHY. 



Chinnock's Cable " Wixdee," or "Spinning Jenny." 
A much more expeditious means, than those described, of 
drawing a cable up to the guard wire, is the Chinnock cable ^ 
"winder," popularly termed the '^spinning jenny." It is shown' 
in cross-section in Fig. 427. The device consists of a bobbin a, 
split in two parts, lengthwise, and having a hole through the 
center as indicated. An end view of the bobbin is given at b. 

The device is employed as follows: The two parts of the 
bobbin are first separated and are then put over the guard wire 
and the cable to be draw^n up to the guard. The parts are then 
fastened together by hooks on the ends of the bobbin, or 




otherwise. The bobbin is now free to be moved along the guard 
wire w and cable c, as indicated in Fig. 428. Strong marline 
is then wound on the bobbin in layers, from one end to the other, 
and thence back to the starting point, and so on. The marline is 
then attached to a support, as at p. A larger rope r is connected 
to the hook h on one end of the bobbin. This rope is then 
h;mled by linemen stationed at suitable points in advance. The 
effect is that, as the bobbin is thus pulled along the guard wire, 
the marline is unreeled from the bobbin and twists itself spirally 
around the guard wire and cable, and, as it progresses, draws up 
the cable in proximity to the guard wire, pushing before it the 
slack of the cable, which is taken up by linemen as it accumu- 
lates. 

This arrangement is extensively employed in this country for 
this purpose. The operation of w^inding the bobbin has, of course, 
to be repeated, between every two points of support. In some^ 
instances the process is repeated, as from p' to p, to give added 
security to the cable. 

The inside of the bobbin is sheathed with copper to prevent 
wearing. The copper is attached to the ends of the bobbin, as 
indicated in end view, b, Fig. 427. 



^) 



^ 



^ 



■^ 



FIG. 42&» 



CHAPTER XXXIV. 

Specifications — Estimates— Miscellaneous — Tables. 
Specifications, Appakatus, Etc. 

The following specifications have been found of service in practice and may, with 
each modifications as changing conditions may require, be of some value as a basis 
for others : 

TELEGRAPH KEY. — (Maker, as may be stated.) Legs two inches long, having 40 
well-cat tlireads to the inch, witli thumb-screw and two washers for each leg, to match. 

MORSE KELAY. — Resistaiicc 150 olims. Silk insulation on copper wire of coils. 
Oiled base, with iron rim around the edge. Screw-posts all on one side. Length of 
core 2i inches. * Diameter of core -^q inch. Length of helix 2^ inches. Length of 
lever of armature 2^ inches. Diameter of helix i^ inches. Iron core must be of 
tlie best soft iron. The copper used in winding same must have conductivity of 
at least 97 j)er cent, of pure copper. 

MORSE LOCAL SOUNDER.— Resistance 4 ohms. Short spiral spring. Sounder must 
give good, clear, snapping sound, without a " ring '' following the stroke. Silk 
insulation on helix. Iron used for cores of magnets and wire wound on them, same as 
for relay. 

REPEAiiNa SOUNDER. — Rcsistancc 4 ohms. Interchangeable contact points. 
Short spiral spring. In other respects same as for ordinary sounder. 

MAIN LINE SOUNDER. — Rcsistauce, 20 olims. Similar in other respects to the 
Morse local sounder. 

POLE-CHANGER. — Coutact points and levers well separated, to prevent the cur- 
rent forming an arc between them. Resistance of electro-magnet, 4 ohms. Silk insula- 
tion. Iron of electro-magnet to be of best quality soft iron, and wire for winding the 
same to have a conductivity of, at least, 97 per cent, of pure copper. Screw posts 
all on one side. Base, same as for Morse relay. 

SINGLE TRANSMITTER. — " Shovcl-uose " coutact touguc. Rcsistaucc of magnets, 4 
ohms. Silk insulation. Iron for electro-magnet and wire for winding same, similar 
to pole-changer, Screw posts all on one side. Base, same as for Morse relay. 

RHEOSTAT, (COMBINATION.) — Scts of coils iu rlicostat sub-dividcd ( as may be 
desired ). The 3,000, 2,000 and 1,000 ohm spools to be wound with, at 
least. No. 34 B. W. G. wire, and no wire smaller than No. 34 to be used in any of the 
spools. Length of rheostat; 10 inches. Width 5.} inches. Height 5 inches. 

SPARK COIL. — Total resistance of coils 1,110 ohms, sub-divided as follows 400, 

553 



554 AMERICAN TELEGRAPHY. 

300, 200, 100, 50, 35, 20, 10 ohm coils. Wire used must not be smaller than Ko. 34 
B. W. G. 

3-P01NT SWITCH. — Length of legs, 2 inches. Well-cut threads on legs, 40 to the 
inch, with thumb-screw and 2 washers to each leg. Polished base. 

EEGULAE RHEOSTAT. — Total resistance of coils 11,110 ohms, sub-divided as follows: 
4,000, 3,000, 2,000, 1,000, 400, 300, 200, 100, 50,30, 20, 10. No wire smaller than No. 
34 B. W. G. to be used in any of the coils. 

POLAR RELAY. — Differential^40o ohms each side. Wires of different coils must not 
be crossed over each other inside the ebonite covering. Permanent magnet, semi-circula)- 
in form, 3 J inches in diameter at the widest point. Length of armature 2^ inches. 
Iron for electro-magnets must be of the best quality of soft iron, and wire for 
winding same to have a conductivity of at least 97 per cent, pure copper. Silk insu- 
lation over copper wire. Sciew posts all on one side. Base same as for Morse relay. 

QUADRUPLEx NEUTRAL RELAY. — Differential — 200 ohms each side. Cores of 
magnets I inch in diameter, and i^ inches long. Light retractile spring. 
Lever of armature 2f inches long. Length of helix ly^g- inches. Diameter of helix 
i|- inches. Quality of iron for electro-magnets and wire for winding same to be as 
called for in the polar relay. Screw posts all on one side. Base same as for Morse 
relay. 

SPRING JACK SWITCH CORD AND PLUG — DOUBLE CONDUCTORS. - Length of '"cord" ac- 
cording to directions of each requisition. Conducting wires of cord to. be composed of 
strands of tinsel wire of good quality, each conductor well separated from the othei , 
throughout. The conducting wires must be neatly and iirmly soldered to the metal 
on handle end of plug, and then covered with strong twine. A piece of ilexible 
rubber tubing, 4 inches long, must cover the junction of the cord and the ])lng. The 
surfaces of the brass on the plug must be well insulated from each other, the plug 
itself to be of good insulating material, such as hard rubber. 



BATTERY MATERIAL. 

BATTERY OIL. — Must be, uon-volatilc, non-inflammable, odorless, not capable of 
crusting, and must be of a color readily distinguishable from the solution, and have 
the quality of spreading well upon the battery solution. Reddish color preferred. 

BATTERY JAR. — Extra well annealed, clear, flint glass. Weight of jar, 3 lbs. Size 
6x7j inches. 

Battery copper. — Made of 98 per cent, pure, well-annealed. Lake Superior cop- 
per, .01 inch thick. Three "leaves," 5|x2|^ inches, concaved on low^er edge, fastened 
together by a rivet in the middle. Well annealed copper connecting wire, .049 incli 
diameter, covered w^itli a gutta-percha compound insulation, -5*2 ii^<^^ diameter, excc])t 
for i^ inches at the top, which must be removed without scratching the wire. Lower 



STECIFICATIONS. 



003 



end of wire doubled on itself for J inch-well fastened to the ''copper'' by a rivet, lialf way 
between bottom and top of one leaf of the copp.^r, near the end. iotal length of con- 
necting wire, 12 inches from top of copper leaf. Weight of copper, with connecting 
wire, 2-| ozs. (The ''insulation" of this copper wire should not be pure gutta-i».'i-cha. 
as, in that case, it is liable to crack, outside of the solution, in a comparatively short 
time; nor a rubber compound, because of the demulscent effect of the battery oil 
upon it.) 

BATTERY ZINC— Crowfoot pattern. Impurities not to exceed -^ of one per cent. 
Hole in "hanger," for connecting wire, -3% inch diameter, and smooth, to prevent sera tell- 
ing the av ire. Zinc to be smooth throughout. Thumb-screw of brass. Well cut 
screw, 20 threads to the inch. End of screw blunt and smooth. Distance from inside 
of hanger to bottom of zinc 2^ inches. Weight 5 pounds. Hole for thninb screw 
to be well threaded, and must match the screw" exactly. 

ZINC AND (COPPER SCRAPER. - One foot iu length. Material, steel. Handle and 
blade one solid piece. Handle 5 inches long, i inch in diameter. Blade 7 inches 
long, flattened out in middle and tapering towards end. Middle of blade i^ inches 
wide. Diameter of b'ade near handle J inch, at middle f inch, at point f inch. 
Blade to be double-edged. Edges about J inch thick. 



Specifications for Hard-drawn Copper Telegraph Wire. 

Weighing 170 lbs. per wile. Weighing J 10 lbs. per mile. 

Gauge No. 12 B. W. G. No. 14 B. W. G. 

Resistance per mile, ohms at 6o°F. 5.23 8,078 ohms 

Weight per mile ohm, at 6o°F. 888 59 888.59 

Diameter, in inches .104 -083 

Conductivity 98 per cent. 98 per cent. 

Elongation i to 1.5 per cent. i to 1.5 per cent. 

Twists in 6 inches 40 40 

Tensile strength 550 lbs. 355 ^^s. 

Bends 3! 3i 

One bend and straightening out counts i. 

(Note, llie tensile strength for other sizes of wire may be placed at three 
and two-tenths times the weight, per mile, of the wire. The resistance or the weight, 
per mile, for other sizes of wire, may be calculated from the weight-per-mile-ohm, as 
explained elsewhere.) 

All wire furnished to be smooth, briglit and polished, round in ^^TOss-section, and 
witliout kinks of any kind. Length of coil at least J mile, without splice, for 170 lb. 
wire. 



556 AMERICAN TELEGRAPHY. 

After having been passed by the purchasers Inspector, each coil to be tied with 
four bands; then thoroughly covered with burlaps, or sacking, and wound with 15 
turns of wire, outside. 



Specifications for Galvanized Iron Telegraph Wire. 

1. "The wire to be soft and pliable, and capable of elongating 15 per cent 
without breaking, after being galvanized. 

2. Great tensile strength is not required, but the wire must not break under a; 
strain less than three times its weight, per mile. 

3. Tests for ductility will be made as follows: The piece of wire will be' 
gripped by two vices, 6 inches apart, and twisted. The twists to be reckoned by 
means of an ink spiral, formed on the wire during torsion. The full number of 
twists must be distinctly visible between the vices on the 6-inch piece. The number 
of twists in a piece of 6 inches in length not to be under 15. 

4. The electrical resistance of the wire in ohms, per mile, at a temperature of 
60 Falirenheit, must not exceed the quotient of the constant number 4844 when di- 
vided by the weight of the wire in pounds, per mile. Examples: A wire weighing 
550 lbs., per mile (No. 6) should have a resistance not exceeding 4844 -•— 550 = 
8.8 ohms, per mile. A wire of 388 lbs. per mile (No. 8) should have a resistance not 
exceeding 4844 -^ 388 — 12.48 ohms, per mile. 

5. The wire to be cylindrical and free from scales, inequalities, flaws, sand 
splits and all other imperfections and defects. 

6. It is desired to obtain the wire in coils, all of one piece, of about 150 lbs. 
each. 

7. The wire must be well galvanized and capable of standing the following test: 
The wire will be plunged into a saturated solution of sulphate of copper, and permit- 
ted to remain one minute, and then wiped clean, ^liis process will be performed four 
times. If the wire appears black after the fourth immersion, it shows that the zinc 
has not been all removed, and that the galvanizing is well done ; but if it has a copper 
color the iron is exposed, showing that the zinc is too thin." 



Specifications for a Telegraph Cable for Aerial or Underground Use. 

No. of conductors as desired. Insulating material as desired. 
Conductors to be No. 16 B.W.G. copper wire. Conductivity 98 per cent. 6 — 32ds 
insulation. Conductors to be in exact center of insulation. 

Electro -static capacity not to exceed .35 microfarad, per mile. 

Insulation resistance of cable not to be less than 500 megohms, per mile, after 



SPECIFICATIONS. 557 

I minute electrification ; test to be made after at least 48 hom-s' immersion in salted 
water, at temperature of 75° F. 

Cn^'le to stand, without deterioration, variations in temperatures ranging from 5°F, 
below, to 15 o°F., above, zero. The whole to be enclosed in jute covering, rinished 
with two thicknesses of rubber tape. 

Outside diameter not to exceed inches. 

• Cable to be warranted, by the manufacturer, for 3 years, to withstand Ciectrical 
pressure of 500 volts; also to be warranted for same period against injury fro?:a gas or 
water, if laid in underground ducts. 



Specifications yor Short Cable foe River or Harbor Crossing. 

Seven or more conductors, each to be No. 16 B.W.G. copper wire; or of 3 wire& 
No. 18 B.W.G. stranded, as may be stated by purchaser. Conductivity, 98 •par cent. 
Outside diameter of each conductor 9-3 zds inch. 

The whole, after cabling, to be well juted aud armored with 18 No. 9 B.W.G. 
galvanized iron wires, or a less number of No 4 B.W.G., depending on conditions to 
be met. 

Insulation resistance of each conductor 500 megohms, at 75^ F. after i minute 
electrification, and after at least 48 hours immersion in water. 

Electro- static capacity, .35 microfarads, per mile. 



Specifications for Emergency Cable. 

(In cases of breaks in the pole line, due to floods, railroad wrecks, etc., a small, 
easily handled cable is of much value in opening up communication pending re- 
pairs of the break.) 

Length of cable about ^ mile. 

Number of conductors, say, 12. (18 B.W.G.) 

Nature of insulation of each conductor to be some tough, pliable material, utterly 
impervious to moisture, such as a rubber compound. Thickness of insulation of each 
conductor, 4-3 2ds. 

Insulation resistance to be at least 500 megohms, per mile, after i minute, electri- 
fication, and after 48 hours immersion in water, at 75° F. 

Cable to contain i taped or tracing wire. 

Two extra heavy tapes outside. 

Outside diameter of cable to be about i7-32ds. 

Cable to be placed on a light reel. 



558 AMERICAN TELEGRAPHY. 

FOKM OF COJ^TRACT SpECIFICATIOX FoR THE MANUFACTURE AnD LaYING OF UNDER- 
GROUND Cables. 

" The cable is to be laid from street, city, along street to 

Avenue under right of way furnished by the Telegraph Company. 

The length of trench required is about feet. 

The cable to contain conductors of copper, of which are to consist 

eacli, of a single wire, having a diameter of of an inch (No. gauge,) and 

one conductor to consist of a copper wire having a diameter of of an 

inch (Xo. Gauge) and a conductivity not less than per cent, of that of 

pure copi^er. 

The insulation to be of the material commonly used by the Insulated Wire 

Com})auy, and to have a diameter of at least thirty seconds of an inch on the 

small wires, and at least thirty-seconds of an inch on the large wire, and shall 

in all cases offer a resistance of not less than megohms per mile. 

The Insulated Wire Company warrants the conductors to maintain the 

above insulation resistance for one year, against an electromotive force of volts 

on the small conductors and — - volts on the large conductor. 

If one or more of the conductors in the cable shall not meet the requirements of 

this agreement then a proportionate amount shall be deducted from the price of the whole 
cable, and cost of laying thereof for such M'ire or wires, and thereupon, the w^ire or 

wires so rejected shall be and remains the property of said ■ Insulated Wire 

Comj^any, and the said Telegraph Company shall have no right or title in or to 

such wires. It is hereby agreed and understood that the Insulated Wire Com- 

]):inv does not warrant against mechanical injury, that is, such injury as might result 
from accidents, excavations, or malicious tampering, etc., and any repairs or replac- 
ing of cable made necessary, by such causes, shall be made by them at the expense 
of the Telegraph Company, at the actual cost of such repairs and replacing. 

The cables are to be laid in a box — inches square on the inside, to be made 

of lumber at least inch thick thick, and filled in with earth; said box to be 

laid in a trench feet deep; the cable to be reeled in the box, joints made, exca- 
vation refilled and all displaced paving replaced, by the Insulated Wire Com- 

panv; said work to be done in a manner satisfactory to the city authorities. 

It is understood and agreed that the price of the above cable shall be 

cents per foot, and that the trenching and repaving shall be done at cents per 

vard, and the box containing the cable shall be cents per foot; and an addi- 
tional sum of dollars per mile shall be allowed on each mile of cable laid in 

said trench or proportionately for any fraction of a mile to cover cost of joining and 
reeling the cable in the trench. All the expenses connected with tlie opening of the 
streets, laying the cable and repaving the streets to be paid as soon as the work 
of laving the cable and repaving the streets shall be completed. And, within 

(lays after notice from the Insulated Wire Company that the line is ready for 

use said cables shall be tested by an electrician appointed by the Telegraph Com- 
pany, and, if found in accordance with these specifications, shall be turned over to them 
for their use, and after days trial, if the cable still continues in perfect order 



MISCELLANEOUS. 



559 



as per these specifications, then per cent, of the price of the cables shall he 

])aid. And if said cable shall continue in perfect working order during the furtlier 
period of days, then at the end of days, said flays, said Tel- 
egraph Company shall pay the remaining per cent, of the price of said cable." 



MISCELLANEOUS. 

BixDixG Screws.- In Fig. 429 are shown several types of binding posts such as 
Ale used on switch boards, relays, etc. 

FI3. 429 







BINDING SCREWS, 

4 !£ & " double connector'' ; ^, c and d are " single connectors.'' b is known as the 

FIG. 430- 





MESSAGE HOOKS. 

«' English '* binding post; it affords a firm contact with the wire and is very suitable 
for permanent connections. 

To prevent loosening of the contact upon the wire, as frequently happens in 
the forms a c d, a " set " screw is generally provided in addition to the ordinary 
screw. 



560 AMERICAN TELEGRAPHY. 

Message Hooks. — " Message " hooks for holding telegrams prior to transmission 
are generally provided on each desk in operating rooms. The style shown at a in 
Fig. 430, is the one most frequently employed. Hooks c and d are designed to pre- 
vent the accidental removal of messages from the hooks : by drafts of wind, etc. 



Peices of Telegeaph Appaeatus, Material, Etc. 

The following figures, while taken from actual quotations and estimates, can only 

be considered as approximately correct; the prices constantly changing. The figures, 
however, will serve to give a fair general idea of present prices. 

Morse key, $1.50 

Sounder, 4 ohms, 2.40 

Morse relay, 150 ohms, 4.00 

Neutral relay, double winding, 200 ohms, ii-5o 

Polar relay, 11.50 

Transmitter, single, 6.75 

Pole-changer, 11-25 

Kepeating sounder, 4 ohms, 2.75 ■ 

Rheostat, 11,100 ohms, i5-oo 

Combination rheostat, 35-oo 

Spark coil, 1,100 ohms, 6.00 

Condenser, 3 to 4 mf, adjustable, 18.00 

3-pGint switch, 0.05 

I zinc, crowfooi, 3 lbs., 0.20 

Blaestone, i lb., 0.03 to .04 

I battery jar, 0x8 inches. 0.14 

I battery, copper, 0.08 to .12 

Rubber tape in rolls, about $1 per lb. 

No. 6 iron wire, about 4 J cents per lb. 

No. 12 copper wire, 14 cts. per lb. 

Cross-arms, 40 cts. each. 

Insulators, 22 oz., 4 cts. 
Creosoted wooden subways, about 16 cts. per foot, per duct, exclusive of excava- 
tion, back filling and repaving. 

Estimated average cost of maintenance of I gravity cell, per annum, $1.16. This 
includes zinc, bluestone, labor, rent, breakage, supervision. 

Carefully estimal ed average cost of maintenance of a telegraph line places it at 
$25 to $30 per mile, per annum. 



Effects of High Tempeeatuees ok Vulcanized India Rubber Insulation. 

The effects of high temperature on vulcanized India rubber is to harden it, and, 
eventually, to carbonize it. Vulcanized rubber will ignite when brought into moderately 
prolonged contact with flame. 



PRICES OF TELEGRAPH APPARATUS, MATERIAL, ETC. 



561 



Tests made by the writer, of India rubber cables which had an insulation resistance 
of 1,500 megohms, per mile, at 60° F., gave the following average results at the tem- 
peratures stated. 

Degrees Fahrenheit Insulation, resistance megohms, 

no 220. 

120 200. 

130 180. 

140 160. 

150 131. 

170 62. 

180 49- 

190 29.7 

200 18.6 

212 114 

The same cables showed the following increase of electo-static capacity: 

cent* 



.he 


temperatures 


of 


100° 


t' an 


d 110° F 


5 


per 


it 


(( 


it 


110° 


(( 


125° " 


5 


a 


ti 


cc 


a 


I2,S° 


« 


140° " 


6 


a 


(C 


K 


it 


140° 


(C 


150° " 


6 


a 


i( 


(i 


u 


iS0° 


'( 


160° " 


6 


<( 


ti 


(t 


it 


160° 


a 


170° '' 


8 


<( 


it 


t( 


u 


170° 


a 


t8o° " 


I-? 


t£ 


cc 


(( 


it 


180° 


it 


100° " 


16 


.:i 


C( 


u 


it 


190° 


'* 


200^ "• 


Tft 


a 


M 


6i 


« 


200*^ 


(S 


gv^" '• 


^O 


«& 



Average Salaries of Telegraph Operators in Different Countries. Compiled by 
Carrol D. Wright, United States Commissioner of Labor, 1901. 



Country. V 


^ages per Day. 


Hours per 
Week. 


Country. 


Wages per Day. 


Hours per 
Week. 


Australia $ 


80 to $2.67 


_ 


Japan 


$ .15 to$ .25 





Belgium 


98 





Mexico 


1.92 


60 


Canada i 


32 to 3.60 


56 


Netherlands 


.50 to .99 


56 


•China 


79 




llussia 


.26 to 3.00 


56 to 84 


Prance 


99 





United States 


1-95 


70 


Germany 


68 to .98 


63 


' ' in large 






Great Britain i 


II to 1.95 


56 


offices 


2. 20 


50 


Italy 


90 


60 


" maximum 


3.00 


54 



In 1850 the highest salaries paid operators in the United States was about 835 
per month. The superintendents of telegraph received about $125. In i860 the 
salary for operators was about $55 per month. During the war, 1S62 to 1S6-. 
these latter salaries were doubled. 



562 AMERICAN' TELEGRAPHY. 

TABLES. 

DIFFERENCE BETWEEN PRINCTPAL WIRE GAUGES IN DECIMAL PARTS OF AN INCH- 



New British 


American. 

or Brown & 

Sharp. 

(B. & S.) 


No. of Wire 
Gauge 


Birmingham 
or Stubs. 
(B. W. G.) 


Washburn & 
Moen. 






000000 




46 








00000 




43 




.4 


' * '.4(3 


\J\J\J\J\J 

0000 


*.45'4"* 


.393 




.372 


.40964 


000 


.425 


.362 




.348 


.3648 


00 


.38 


.331 




.324 


.32495 





.34 


.307 




.3 


.2893 


1 


.3 


.283 




.276 


.25763 


2 


.284 


.263 




.252 


.22942 





.259 


.244 




.232 


.20431 


4 


.238 


.225 




.212 


.18194 


5 


.22 


.207 




.192 


.16202 


6 


.203 


.192 




.176 


.14428 


7 


.18 


.177 




.16 


.12849 


8 


.165 


.162 




.144 


.11443 


9 


.148 


.148 




.128 


.10189 


10 


.134 


.135 




.116 


.090742 


11 


.120 


.12 




.104 


.080808 


12 


.109 


.105 




.0^2 


.071961 


13 


.095 


,092 




.08 


.064084 


14 


.083 


.08 




.0'2 


.057068 


15 


.072 


.072 




.0«4 


.05082 


16 


.065 


.063 




.056 


.045257 


17 


.058 


.054 




.048 


.040303 


18 


.049 


.047 




.04 • 


.03539 


19 


.042 


.041 




036 


.031961 


20 


.035 


.035 




.032 


.028462 


21 


.032 


.032 




.028 


.025347 


22 


.028 


.028 




.024 


.022571 


23 


.025 


.025 




.022 


.0201 


24 


.022 


.023 




.02 


.0179 


25 


.02 


.02 




.018 


.01594 


26 


.018 


.018 




.0164 


.014195 


27 


.016 


.017 


r 


.0148 


.012641 


28 


.014 


.016 




.0136 


.011257 


29 


.013 


.015 




.0124 


.010025 


30 


.012 


.014 




.0116 


.008928 


31 


.01 


.0135 




.0108 


.00795 


32 


.009 


.013 




.01 


.00708 


33 


.008 


.011 




.0092 


.006304 


34 


.007 


.01 




.0084 


.005614 


35 


.005 


.0095 




.0076 


.005 


36 


.004 


.009 




.0068 


.004453 


37 




.0085 




.006 


003965 


•J 1 

38 




.008 




.0052 


• yjyj'^ fj \j *j 

003531 


39 




.0075 




!0048 


.003144 


40 




.007 





TABLE OF 



'-'i 



Number, Diameter, Weight, Length and Resistance of Com 

MERciAL Copper Wire. 

FERCENTAGE CONDUCTIVITY 98. 













j 


Resistance 




Gauge' Diam. 


i Weight. Sp. Gr.— 8.889 


; Length. 


1 


at 70° Fahrenheit. 
B. A. Ohms. 




^ Sj In mils. 


Grs. 

per ft. 


: Lbs. 
per 

: 1000 ft. 


: Lbs. 

: Pf^ 

: mile. 


: Feet 
per lb. 


Ohms ; 
per ; 

ICOO ft. ; 


Ohms : 
MHe. 1 


Feet : 
Ohm 


Ohms 
per lb. 


00G0;460.000;4475.33 


'' 639.33 


3375.66 


1.56 


.051! 


.269219605.69: 


.0000798 


000:409.640:3549.07 


507.01 


2677.01 


1.97 


.064! 


.337915547.87; 


.000127 


00364 800:28 14.62 


402.09 


2122.93 


2.49 


.081: 


.427612330.36; 


.000202 


0324.950:2233.28 


319.04 


1684.53 


3.13. 


.102! 


.5385 


9783.63! 


.00o:.20 


1289.3001770.14 


252 88 


1335.20 


: 3.95: 


.129; 


.6811! 


7754.66! 


.00051 


2:257.630:1403.79 


200.54 


1058.85 


4.99; 


.163; 


.8606, 


6149 78! 


.000811 


3229.42011113.20 


159.03 


839.67 


6.29i 


.205; 


1.0824 


4876.73! 


.001289 


4i204.310; 


882.85 


126.12 


666.00 


7.93! 


.259: 


1.3675 


3867 62; 


.00205 


51181.940: 


700.10 


100.01 ; 


528.05 


10.00! 


.326! 


1.7212: 


3067,06! 


.00326 


6il62.020; 


555.20; 


79.32 : 


418.60 


12.61! 


.411! 


2.17oOi 


2432.22! 


.00518 


71144.280: 


440.27 : 


62.90 : 


332.11 


15.901 


.519! 


2.7973, 


1928.75! 


.00824 


81128.490; 


349.18 ; 


49.88 ; 


263.05 


20.05! 


.654! 


3.4531! 


1529.69! 


.01311 


9:114.430: 


276.94; 


39.56 : 


208.87 


25.281 


.824! 


4.3507: 


1213.22: 


.02083 


101101.890; 


219.57: 


31.37 ; 


165.70 


31.88! 


1.040! 


5.4912! 


961.91! 


.03314 


Hi 90.742: 


174.15^ 


24.88 ; 


131.50: 


40.20! 


1.311! 


6.9220; 


762.93! 


.0526if 


121 80.808: 


138.11; 


19.73 ; 


104.20 : 


50.69! 


1.653: 


8.7278; 


605.03: 


.08377 


131 71.961; 


109.52: 


15.65 ; 


82.74: 


63.9li 


2.084! 


11 0035! 


479.80! 


.13321 


14i 64.084; 


86.86; 


12.41 : 


65.51 ! 


80.59! 


2.628! 


13.8758! 


380.51: 


.2118 


15i 57.068; 


68.88! 


9.84! 


51.95; 


101.63! 


3.314! 


17 4979! 


301.75; 


.3368 


161 50.H2(>: 


54.63 ; 


7.81 ; 


41.27 ! 


128.14i 


4.179! 


22 065 ; 


239.32; 


.5355 


17i 45 257: 


43.32 ; 


6.19; 


32.72 ! 


161.591 


5,269; 


27.820 j 


189.78: 


.8515 


181 40.303; 


34.35 ; 


4.91! 


25.96 : 


203.761 


6.645! ^ 




150.50! 


1.3539 


19i 35.3901 


26.49 ; 


3.88; 


20.58 ; 


264.26i 


8.617! 


I 


116.05! 


2.2772 


20i 31.961i 


21.61 : 


3.09; 


16.36 ! 


324.00'- 


10.566: 


i 


94.65; 


3.423 


21! 28.462; 


17.13; 


2.45: 


12.94 ; 


408.56 


13.323! 


; 


75.06! 


5.443 


22i 25.347; 


13.59; 


1.94; 


10.27 ! 


515.15 


I6.799; 




59.53! 


8.654 


23; 22.571; 


10.77 ; 


1.54; 


8.14; 


649.66^ 


21.18^: 




47.20: 


13.763 


241 20.100; 


8.54; 


1.22; 


6.45; 


819.21! 


26.713! 


i 


37.43! 


21.885 


251 17.900; 


6.781 


.97! 


5.12! 


1032.96 


33.684! 




29.69: 


34.795 


261 15.940; 


5.37; 


.77: 


4.06! 


1302.61: 


42477! 




23.54! 


55.331 


27i 14.195! 


4.26; 


.61! 


3.22! 


1642.55 


53.563! 




18.68! 


87.979 


28i 12.641; 


3.38; 


.48! 


2.55! 


2071.22 


67.542! 




14.81; 


139.893 


29^ 11.257; 


2.68; 


.38; 


2.02! 


2611.82 


85.170! 


.x5.28 j 


11.73 


222.449 


30! 10.025; 


2.13; 


.30! 


1.60! 


3293.97i 


107.301! 




9.31! 


353.742 


31! 8.928; 


1.69; 


.24; 


1.27! 


4152.22! 


135.402! 




7.39! 


5(>2.22] 


32! 7.950; 


1.34; 


.19! 


1.01! 


5236.66 


170.765! 




5.86! 


894.242 


33! 7.080; 


1.06; 


.15; 


.80! 


6602 71: 


215.312! 




4.64^ 


1421.646 " 


34! 6 304; 


.84; 


.12 ! 


.63! 


8328.30! 


271.583! 




3.68! 


22()1.82 


35! 5.614; 


.67! 


.10! 


.50:10501.35; 


342.443; 




2.92: 


3596.10 


36i 5.000; 


.53; 


.08; 


.40 :13238.83: 


431.712! 




2.32: 


5715.36 


37! 4.453; 


.12; 


.06 ; 


.31 :16e91.06 


544.287! 


1 


1.84: 


9048 71 


38! 3.965; 


.34; 


.05! 


.25 :20854.65: 


686.511^ 


I 


1.46 14320.-6 


39! 3.531; 


.27; 


.04 i 


.211:26302.23: 


865.047! 




1.162 


2752.6 


40^ 3.144; 


.21! 


.03 1 


.158 ;33175 40 1091866;] 


] 


.92 3 


6223 59 



550 (+ 88 + xvi = 668 pp.) 

SUPPLEMENTAL INDEX. 



A M 

Alphabet, Myer, 363. • 

" Buckingham, 436&. 

Ahiminum armature levers, 187. 
Ammeters. 120, 148. Ampere hours, 49&, 49c. 
Ampere turns, 33, 318. 
Angle of lag, 100a. 
Automatic cut-out. 49<:^. 

telegraphy, Delany, 321&, 322. 
Pollak-Virag, 3236. 

" transmission, 72. 285. 

"• embossed tape for, 72. 

"• switches. Ib6rf. 

Eittery. dry, 3:]5: Edison, .35.5&. 
Bloc l<; signals, railway, wireless system for, 508a. 

Miller cab signal, 508a. 
Branlv coherer. 3356. 
Buckinghaoi alphabet, 4366. 
piinter, 436a. 
Biirry self-winding ticker, 419. 
Buzzer working, 366a. 
Capacity uniformly distributed, lOOe. 
€atch magnets, .508a. 
Choke coils, 335^i. 
€ode, see Alphabet. 
Coherer, anti. auto, 3.3.56, .335/, .3.35^. 
Condensers in bridge duplex, 212, 321. 
Conductors, loaded. Thompson, Pupin, 100€. 
Counter e. m. f.. 100a. 
Current for relays, 69. 
Dead beat swing, 119. 
De Forest wireless telegraph, ,3.35^'. 
Delany automatic telegraph, 3216. 
Diehl "test for crosses, 142. 

Double current method, repeaters, 166<?, 167, 3216. 
Duplex, high potential leak, 255. 
Electric "eve,"" waves, undulations, 335a. 
Electroeranh, .323. 

Electromagnetic theory *of light. 3.35a. 
Electromotive force, connfer: impressed, 100a. 
Electronic theorv. electrons, 3. 
Energy, e. m. f. lOOa; kinetic, 100/ ; radiated, ,335^ 
Ether, 3, 335a. 
Field key system, 226. 

Fleming wireless transmitting system, 3351. 
Erequency, 1006. 
Euses, 87, 89. 

Galvanometer. D'Arsonval, 119. 
Gray's harmonic telegraph, :3.5.5a. 
Oroiind for vertical wire, .3;35/. 
Henry, unit of inductance. 1006, 207a. 
Hertz experiments, oscillator, waves, 335a, 3356. 
Horse-power. 8. 

Hughes printer, relay, 240c, 436. 
Impedance, 1006. 
Increment key, 2406. 
Inductance, see Self-induction. 

of relays, etc., 100/", 318. 

" uniformly distributed, 100/". 

Induction telegraph, 335. 
Inierjjolator, 2856. 
Interrupter, .335. 
Iridium coatact, 28.5a. 
Iron poles for semaphores, 508. 
Keeper, 240c. 

Key or transmitter, reversing, increment. 2406. 
Leak box, 223. 
Xeak relay, 166c?. 

Lightning arresters, carbon, argus, fuses, 89. 
Lines of force, 33. 
Local correction device, 2856. 
Magnetic lines of force, 400. 

" flux, saturation, permeability, 33, 66. 
pull, 240c. 
Magnetism, Ampere theory of, 66. 
Marconi wireless telegraph, 335c. 
Master switch, 332, 
Miller cab signal. 508a. 
Morris duplex, 268. 
Morse sending, notes to beginners, 576. 

" manual transmission, advantages of, 57c?. 
Motors, motor dynamos, motor generators, 49a. 
Myer alphabet, 363. 



O Z 

Ohm's law, lOOcZ, lOO^'. 
Oscillations, rate of. 33.56. 
Oscillators, Hertz, 3356. 
Penmanship, 57c. 
Perforator, keyboard, 321a, 436a. 
Photographic receiver, 3236. 
Polarized relay, 186. 
Poles, iron, for semaphores, 508. 
Pollak-Virag automatic telegraph, 3236. 
Preece induction telegraph, ,335. 
Printing telegraph, Buckingham, 4.36a. 
" " Hughes. 436. 

" " Baudot, Rowland, 4363', Barclay, 437. 

" "■ Burry. 419; Muriay, A'd-nl. 

Punch magnets. 4.36cif. 
Pupin loaded conductor, lOOc. 
Quadruplex, British post-office, 240/*. 

Roberson. 240. 
Railway block signals, 508. 
Reactance. 100, 101, lOla, 100c?. 
Receiving pen. 332. 
Relay, see Repeaters. Direct repeating relays, 255, 

•' " current for. 69. 

" Hughes. 240c. 

" polarized. 33.5c?. 

'' Stroh. 186. 

"• vibrating, ,332. 
Repeaters, Brown cable relay, 285a. 

Atkinson, Ghegah, open circuit, 'IcnV'^ current. 
Repeating sounder, 240c/. il66, 167. 

Resistance, carbon, non-inductive, 2406. 
Retardation of signals, 100. 
Rheostat, Varley, 223. 

Self-induction, 100. 1006, 100c, lOOf, ,318, 321., 335^ 
Semaphores, compressed gas for,"508a. 

motor operated, iron poles for, 508 
Sieurs diplex, 240. 
Signal corps "• kit," ,366a. 
Signaling between vess^els. distance, ,3,35<z 

speed of, 32;i6, 321a, 4,36?/;. 
Solenoid, 66. 

Stevens perforator and transmitter, 321(jt- 
Storage battery, 49a ; chloride cell, 496. 

"■ "• in telegraphy, 49c?. 

Stroh relay. 186. Stumm added resistor c-. ;:i^6. 
Sunflower, 436a. 
Tailings, 322. 
Tapi)er, ;i35c. 
Telautograph, 3,32. 
Telegraph and telephone working, 366a. 

" automatic, 322. 

" Gray's harmonic, 355a. 

" wireless, 332. 

" writing, .3-32. 
Telegraphing pictures. 323a. 
Telephone receiver, 32,36, -335. 

long distance, 3357i. 
Tests by ammeter, voltmeter, 148, 
Time constant. 207a. 
Transmitter, Stevens automatic, 321a. 
Unit of electrical energy, 8. 
United States signal corps kits, 366a, 366c. 
Varley, opacity of magnets, rheostat, 223, .321- 
Vector sum, 100c. 

Velocity of wave propagation, lOOc, lOOf, 101 
Vertical wires, 33.5c, 3a5e. 
Vibrating relay, 3,32. 

" strings, 100^. 
Voltmeters, tests by, 120, 148. 
Wages of operators, 561. 
Watt, kilowatt, 8, 100a. 
Wave, attenuation factor, constant, 100c. 

" propagation, 33.5A, 3.35i. 
Wig-wag telegraph, code, 363. 
Wireless telegraphy, 3;i3 ; syntonic, ,335/: 
De Forest. ,33.5A-. " 

" " Lodge, Marconi, ,3,35c, 335^ 

" " masts for. mbl. 

" " Preece, ,335. 

" " tuned circuits, 335^. 

Zero, wandering, 285. 
Zinc, wasteless, 26. 



1 N- D E X . 



AB 

A'bsolute block signals, 494. 

Absolute units, 7. 

Action ol condenser as static compensator, 209 . 

" Added " resistance, 231. 

Adjusting Morse relay, 63. 

'J Wbeatstone relay, apparatus, 304, 319. 
Aerial cables, 550. 

*' banger, 551. 

" methods ol suspending, Cbinnocks, 

551-552. 
Aerial wires, .ioints on, 545. 
Alpbabets, Morse, Com inental, Bain, Pliilliiis, etc., 

56, 57, 268, 273, 363. 
Alternate current machine, ;j6. 
Amalgamation of zinc, 18. 
Americaa district telegraph messenger service, 

367. 
American standard wire gauge. 514. 

for telegraph wires, 522. 
Ampere, 5. 

turns, 66, 67, 68, 69, 318. 
Anchor guy, 536. 
Anti-hum device, 546 . 

Answer back signals, 370, 374, 376, 464, 480. 
Apparatus, Morse telegraph, 58. 
" prices of, eic, 560. 
" specifications for, 553. 
Armatures, 38, 51, 499. 
Arrangement of dynamo machines in telegraphy, 

44. 
Arresters, lightning. See Lightning Arresters. 
Artificial line, 176. 

" cable, Stearns'. Muirhead's, 276, 279. 
Astatic galvanometer, 112. 
Atlantic cable, 281. 
Automatic answer back, 490. 

" burglar alarm telegraphy. See Burglar 

Alarm Telegraph. 
" fac-simile telegraph, 321. 
" fire-alarm telegraphy, SeeYivQ alarm Tel- 
egraph. 
" multiple transmitter, 476. 
" telegrajih repeaters. See Repeaters. 
*' telegraph sender, 71. 
" telegraphy, Anderson, chemical, Wheat- 
stone. 289, 293, 296. 
Auxiliary fire alarm telegraph, 445, 461. 

Balancing cable duplex, 280. 
" polar duplex, J89 

" quadruplex, 232. 
•' relays, 236. 

" Stearns' duplex, 179. 

•' Wheatstone duplex, 319, 

Barraud and Lund clock synchronizer, 358. 
harrett chloride of silver battery, 18. 
Batteries, A'eeCell. 

" testing condii ion of, 134. 

Battery, arrangement of cells in, 23. 
" copper, 554. 
" copper, zinc, 80. 
" gauge, Bunnell's, 119. 
" internal resistance of, 15. 
" Intermediate, 80. 
" jar or cell, 12, 554. 
•• Lockwood, 377. 
•' material, 554. 
•* oil, 14, 21, 238, 554' 
*• primai'y, 9. 
•• zinc, 554 
Bi-metallic thermostat, 470. 
Binding posts, 79. 559. 

Block-system, See Railway Electric Block Signals, 
494. 
" instrument, Hall's, 503. 



BO 

Bluestone, 11, 12. 
Box relay, 65. 
Brackets, 537, 

, line, 537. 
Branch office signaling devices, Chicago,New York, 

Hurd, 257, 258. 
Brush, dynamo, 36. 
Breakage of cells, 15. 
Breaking strain, 516, 522. 
Breaks in copper wire, 545 
Break-wheels, 368, 468. 
Bridge arms, ratio of, 519. 
•♦ duplex. 172. 
" Wheatstone, 122, 519. ' 
Bridle or jumper, 546. 
British association ohm, 522. 
Brown and Allen relay, 281. 
Bulen automatic fire alarm telegraph, 467. 
Bunnell key, 59. 

" sounder-resonator, 76. 
Burglar alarm and district call box combination, 

386. 
Burglar alarm telegraph, 380, 

Holmes', 380. 
Wilder, 383. 



Cable, artificial, 276. 
" box, 548. 
" duplex, 280. 
♦• emergency, 557. 
'• hansrer, 551. 
*= jointing, 526. 
•• winder, Chiunocks, 552. 
'• working, duplex, simplex, 277,276. 
Cables, aerial. See Aerial Cables. 
" river and harbor, 5-28. 557. 
" specifications for, 556, 557. 
" underground. See Underground Tele,?rapi 

Cables. 
" underground, form of contract for construe 
tion and laying of. 558. 
Callaud or gravity cell, care of, 11, 12. 
Call box, 367. 

" Field and Firman, 472. 
Fix. 387. 
multiple, 373. 
Cant-hooks, 535. 
Capacity, electric, 91. 

" constant of, 132. 
" electrostatic, 91. 
'• of condensers, joint, total, 94. 
" Atlantic cable, 92. 
♦< overland telegraph wires, 92. 
" specific inductive, 91. 
" tests, 131, 142. 
Carbon, resistance under pressure, 326, 345. 
Caution signal, 494. 
Cell, (primary), 9. 
" drv, 21. 
" Burnley, 22. 
" bi-chroinate of potash, 18. 
" Callaud or gravity, See Gravity Cell. 
" chloride of silver, 19. 
" constant, 10. 
" Dauiell's, 11. 
" Edison-Lalailde, 20, 534. 
" Fuller, 17. - 
" Gassner, dry, 23. 
•' Leclanche, 16. 
" open, closed, circuit, 10. 
Cells, arrangement of in batteries, in multiple, i« 

opposition, iu series, 23, 24, 25. 
Charge, static. Sec static. 

" distribution of in conductor, 97. 



Chemical automatic telegraph, See Automatic Tele- 
graphy. 
" action of current, 530. 
" recorder, 294. 

solutions, 290, 295. 
" terms, 9. 
Chemically prepared paper, resistance of, 291. 
C. G. S. units, 8. 
Chicago police patrol telegraph system, 481. 

" branch office signal, 257. 
Chlorides, of zinc, 9, 16. 
Chinnock's cable winder, 552. 
Chronograph, electric, 357. 
Circuit, 51. 

" closed, open, methods, 54. 
«• ground return, 52. 
'* local, 53. 
•' magnetic, 32. 
'♦ metallic, 52. 
" Morse, 52. 
" phantom, 231. 
" short, 10. 
(Circuits, joint resistance of, 27, 30, 146. 
Citizens key, 472. 
City construction work, 546. 
Climbers, 542. 
Clock block signal, 499 
Clocks, electrically synchronized, 358. 
Codes, telegraph, 53, 363. 
Coil, spark, 177. 

Coils, German silver, 42, 101, 178. 
" differential induction, 231. 
" magnetic, 35 1, 480. 
*' resistance, 174. 
" retarding, 177. 
Combination duplex systems, 264, 
" rheostat, 214, 

" plftte and spider lightning arrester, 86. 

Come-alongs, 543. 
Commutator, 37 
Compensating line, 176. 

" condensers. See Condenser. 

Component forces, 1U3. 
condenser, 90. 274, 275. 

" adjustable, 93. 

" as static compensator, action of, 177, 

209, 306, 307. 
" as neutrallzer of reversal effects, 204, 

206. 
«' as neutrallzer of extra-current effects, 

319. 
" capacity of, 91, 93. 

« in automatic telegraphy. 293. 

*' in induction telegraphy, 334. 

•* in multiplex telegraphy, 342. 

«« in printing telegraphy, 401. 

" in simultaneous telegraphy and tele- 

phony, 348. 
" in submarine telegraphy. 275. 

" Wheatstone automatic, 306, 3i5. 

Oonductivit3% conductance. 29. 
" percentage, 518. 

" specific, 518. 

Conduits, See Underground Conduits. 
Constant cells, 10. 

" of capacity, 132. 
" of galvanometer, 144. 
Construction and maintenance of telegraph lines, 
532. 
" after, 648. 

Continental alphabet, 56. 
Continuity preserving transmitter, 176. 
Convolutions of wire in relays and sounders, 69. 

effect of increased number of, 36, 69. 
Copper, manufacture of, etc., 511. 
•' battery, scrapings of, 554, 16. 
" connecting wii'e, 554. 

" wire, hard-drawn, ISee Hard-Drawn Copper 
" tables concerning, 563. 
Cord, double conductor, 79, 554. 
Core, 37, 52. 
Correcting devices, 338, 391. 

relay, 338. 
Corrections for temperature, 520, 521. 
Coulomb, 91. 
Counter, E. M. ¥., 10, 11. 
Creeping salts, 14. 



ODE 

Crosses, locating, 134. 
Cross-arms, 537. 
Crow-foot zinc, 12. 

Current, alternating, continuous, direct, 36. 
distribution of, 30. 
" "excess," 200. 
" magnetizing, 185, 208. 

single, double, methods, 183. 287. 
" strength, 5. 

ratio of, 207, 217. 
Currents, earth, 274. 

pulsatory, 265. 
Cutting lines of force, 33. 
Cuttriss' magnetic siphon recorder, 271. 
Cut out, way-ofQce, 83. 

"Danger" signal, 494. 

Daniells' cell, 11. 

Davis loop switch, 262. 

Dead-man or butt-prop, 534. 

Decrease of current method, 196. 

Delany line adjustment, 150. 

Delany synchronous telegraph, 336. 

Denison automatic fac-similo telegraph, 322. 

Derivation of electrical units, 6. 

Detector galvanometer, 113. 

Dial rheostat, 316. 

Diameter of-wire, tests for, 514. 

Dielectric, 91. 

Difference of potentials, 4, 5, 10, 208. 

Differential duplex, 169, 176. 

galvanometer, 114, 305. 
" induction coil, 228. 

relay. 170. 
Diplex, Sieurs, 265. 
Direct current machines, 36. 

deHection method of testing, 131, 145, 529, 530. 
Disc signal, 499. 
Discharge key, 131. 

Distribution of current in divided circuits, 30, 219. 
District telegraph service, Amei'ican, 367. 
Divided circuits, 30, 219. 
"Dot" key, 398. 
Double-balanced relay, 387. 

" block, Muirhead's, 279. 

" conductor cord, 79, 554. 

" " binding posts, 79, 559. 

" current method, 183, 287. 

" petticoat insulator, 540. 

" spring-jack, 79. 
Drawing in and out conduit, 524. 
Dry batteries, Burnley, Gassner, 21, 22. 
Duct, See Underground Cunduits. 
Ductility tests, 51 7, 555. 
Duplex telegraphy, 169. 

" telegraph, bridge, 172. 

" " cable, 277, 280, 

" " differential, 169. 

'« " Edison-Smilh, 264. 

« " Jacobs, 283. 

polar, 174, 181, 184. 
Stearns', 173. 

" " Varley-Athearn, 351 

" " "Wheatstone, 305. 

Duration of gravity cells, 13, 378. 
Dynamo machine (in telegraphy), 27. 

" " essential parts of, 39. 

" " . methods of arranging, 40, 44, 46, 49. 

theory of, 32. 
loop switch, Davis, 262. 

" pole-changer. 194. 

" reversing switch, 42. 

Earth currents, 274. 
Earth's magnetism, 103. 

directive influence, 112. 
Edison conduit, 524. 

" dynamo machine, 39. 
Lalande cell. 20, 354. 
" phonoplex, 353. 
" Smith duplex, 265. 
" ticker, 406. 
Effects of impurities in metals, 517, 518. 

" of temperature on conductors, on liquids, 

520, 16. 
" of high temperature on vulcanized India 
rubber, 560. 



EFG 

Electrical units, 8. 

Electric block signals, See Railway Electric Block 

Signals. 
Electrical testing, 122. 

" tests of telegraph wir«», 517, 519. 
Electrically synchronized clocks, 358. 
Electrification, 91, 529. 
Electricity, 1. 

positive, negative, 3, 91. 
static, 91. 
Electro-chemical difference of potential, 10. 

" magnet, 50, 

« magnetic mutual induction, 99. 

" motive force, i, 34, 35. 

«-- " " measurement of, 133. 

" pneumatic block signal, 495. 

" static capacity, 91, 95, 267. 

" mutual induction, 99. 

" thermic lightning arrester, 87. 
Electrolyte, 10, 29u. 
Electropoion, 18. 
Elongation of wire, 510, 517. 
EDKlish binding post, 559. 
Escapes, locating, etc., 134, 142, 150, 153. 
Essick page and line printing telegraph, 430. 
Etheridge transmitter, 327. 
Extra current of self-induction, 100. 

" " neutralizer, 319. 

Extended locals, 244. 

Tac-simile telegraphy, 321. 

Fall of potential, 96. 

Farad, 91. 

Fault indicating apparatus, 461. 

Faults, breaking down of, 529. 

" in cables, locating elpctro-mechanically, 530. 
" in quadruples, locating, etc., 232. 
" in telegraph wires, locating, 134, 142, 379. 
Fetter drive screw, 542. 

Field and Firman electric call box, 374, 472. 
" key system, 217. 
" magnet, 38. 
" magnetic, 32. 
Figure of merit, 307. 
Fix call box, 387. 
Fire alarm indicator, 450. 
" " telegraph, 437. 
«' " " auxiliary, 445. 

«« " " boxes, 438. 

" " •'■ Bulen's automatic, 467. 

" " •' Gaynors, 453. 

" " " Gamewell, 440. 

" '« " Jersey City or Speichers, 456. 

• ' " " non-interfering boxes, 438. 

" " " repeaters. See Repeaters. 

Flag signaling, 362, 363. 
Flash " 365. 

Flour as a lubricant, 516. 
Foot-plate, 535. 
Force, 1. 

Force, electromotive, 4, 34, 35, 133. 
lines of. See Lines of Force. 
" magneiizing, 32. 
" resultant, 103. 
Forces, parallelogram of, 105. 
Fonr-round fire alarm boxes, 439, 44T. 
>'reir neutral relay, 207. 
Full r cell, 17. 
Fuaes, 46. 

Gains, 535, 537. 
Galvanometers, 103, 144. 

" astatic, 112. 

" constant of, 144. 

♦' detector, 113. 

♦♦ differential, 114, 305. 

" readings, 529. 

" shunts, 116, 519. 

tangent, 103. 
" Thomson reflecting, 114, 519. 

W. U. tangent, 110. 
fralvanoscope, 103. 
Gamewell automatic repeater, 454. 

auxiliary fire alarm telegraph, 461.. 
" fire alarm telegraph, 453. 

police signal telegraph, 472. 
Galvanizing Iron wire, 511, 512. 



G H IJ K 

Gardiner non-interfering fire alarm box, 445 
Gassner dry cell, 22. 
Gauges, wire, 514, 515, 562. 
Gayiioi fire alarm telegraph, 453. 

" signaling key, 454. 
Geneva stop, 404. 

German silver resistance coil«, 42, 101, 178. 
Gold and stock ticker, 395, 398. 
Governor, Phelps motor, 420. 

" Wbeatstone. 304. 
Gravity cell, battery, 11. 

care of. life of, 12, 12, 16, 378. 

" modification of, 16, 

" use of oil an, 14- 
Gramme, 8. 

Ground retu^'n circuit, 52, 
Grounds, locating, 134. 
Guard wire, 551. 
Gutta-percha, 526, 528, 529. 
Guying poles, 536. 

Guy, anch'jr, double-head, head, side, stub, wire^ 
530. 

Hall's " block " instrument, 500. 

electric signal for railway crossings, 503 
" railway signal system, 494. 
" track " instrument, 500. 
Hamblet clock synchronizer, 3.:9. 

time telegraph, 356. 
Hard-drawn copper wire, 510, 513, 555. 

" breaks in, 548. 
" " first extensive use ot54S. 

Hart's train signal, 507. 
Head guy, 5;J6. 

Healy arrangement of quadruplex, 228, 
■•clutch," 414. 
" locker circuit. 414, 
Heliograph, MacGregor's, 361. 
Heliograpliy. 381. 
Helvin sleeve joint, 545. 

tie, 544. 
Holmes burglar alarm telegraph, 386. 
House-top fixtures, 547. 
Hydrometer, 13 

Impurities in metals, P18. 

Indicator, electro-mechanical, 450, 475. 

Induction coil, 99. 

" differential, 228. 
Induction, electro-magnetic electro-static, self, 99, 
10i». 
telegraphy, 333. 
Inductive capacity, specific, 91, 267. 
India rubber,.spe Rubber. 
Ink recording Morse register, 70. 

automatic telegraph, 287. 
Insulation, 524, 530. 

Insulation resistance of wires and cables, measur- 
ing, etc., 142, 145, 
Insulators, essentials of, 538. 

" B. & O., double petticoat, pony, rubber, 

W. U., tree, 539, 540, 541, 542. 
measuring insulation resistance of, 149 
" tying wire t^, 544. 

Intermediate battery, 80. 

•' or way stations, 54. 

Internal resistance of batteries, 15. 
International, or Continental code, 368. 
Interlocking magnets or relays, 503 
Iron and steel wire nomenclature, 523. 
Iron poles, 532. 
Iron wire joint, 545, 

manufacture of, 511. 

Jacobs duplex, 283. 

Jt-rsej^ City, cr Spelcher fire alax'm telegraph, 456. 

Jockey roller, 299, 423. 

Johnstone conduit, 526. 

Joint resistance, 27, 142. 

" sleeve, 545. 
Joints, cable, 526. 

" iron wire, 545. 

«« measuring Insulation resistance of, 526. 
Jones' arrangement of quadruplex, 226. 

" three-magnet neutral relay, 226. 
Jumper, 546. 
Kerite cable, 526, 



KLM 

Key, citizens, for fire alarm boxes, 472. 

" discharge, 131. 
, " Gaynor signaling, 454. 

•' pole-changing, 341. 

" Morse telegrapti, Bunnell, legless.self-closlng. 
iiteiner, Victor, 59, 60, 61, 553. 

" reversing or tapper, 269. 

" board transmitters, 392, 398, 407, 411, 430. 

" systems, dynamo, quad, 217, 226, 230. 
gravity battery, 198, 212. 

La Cour wheel, 336. 

La Dow telegraph transmitter, 75. 

Lalande-Edison cell, 20. 

Law, Ohm's, 5, 25. 26, 31, 68, 112. 

" of tangent galvanometer, 104. 109. 
" Leak," 231. 

" resistance, 309. 
relay, 309. 
Leclanche ceil, 16. 
Legal ohm, 522. 
Legless key, 61. 
" Letter" key, 398. 
Lightning ai'resters, 84. 

combinatiou plate and spider wire, 86. 
" electro-thermic, 88. 
" magnetic, 87- 

pole, 537. 
" quadrupleXj 
Line adjusiment, Delany's, 150. 
Line repairing, 549. 

Lines of force, 32, 33, 40, 51, 103, 109, 270. 
Local battery, circuit, sounder, 53. 
Locating faults in telegraph wires, See Faults and 
Electrical Testing. 
" " cables, 530. 

" " " point to point method, 530. 

" " " under-running method, 531. 

•'Locker " circuit, Healy's, 414. 
Lockwood battery. 377. 
Loop switches, 260. 

Davis. 263. 
" jK)sta], 261. 

•• test, Varley, 140, 

Machine, dynamo electric.Afee Djnamos Machines. 
MacGregor's heliograph, 361. 
Mam line, 33, 67. 

relay. 53, 63. 
" sounders, 67. 
" office switch boards, 77. 
Maintenance of telegraph lines, cost of, 532, 549, 561. 
Manholes, subway, 526. 
Manual repeaters, See Repeaters. 
Magnet, electro, 33, 50. 

directing, 119, 519. 
interlocking, 503, 
" permanent, 112, 184, 
" polarity of, 181, 20r. 
press, 393. 
Magnetic circuit, 32. 33. 
"circle," 396. 
" coil, 351, 480 
field, 32, 33. 
" lightning arrester, 87. 
" needle. VII, 103. 
" saturation, 66. 
" storms, 274. 
" strength, 69. 
Magnetism, Earth's 103, 
Magnetizing current, 185, 208. 
Manufacture of iron and copper wire, 511. 
Margin, quadruplex working, 231. 
Marking current, 304. 
Mechanical tests of telegraph wires, 514. 
Measurement by Wheatstone bridge, 126, 519. 
" of electromotive force, 133. 

•' of joints, 527. 

Mensur^n^ internal resistance batteries, 134. 

" Insulation resistance of wi';es and 

cables, 142, 529. 
•* partial insulation resistanf^e of tele- 

graph wires, 13U. 
*• resistance, by substitution method, 130. 

'• " Wlieatstone bridge me- 

thod. 126, 519. 
" resistance of insulators, 142. 



M N O P 

Megohm, 144. 

plate, 146. 
Message hooks, 559, 

Metals, impurities in, effects of, 517, 518. 
Metallic circuit, 52. 

Methods of arranging dynamos in telegraphy. See 
Dynamo Machines. 
" suspending serial cables, 5.50 
" telegraphing, open, closed circuit, 54. 

55. 
'• telegraphing, single, double current. 
183, 287. 
Microfarad, 92. 
Micrometer gauge, 515. 
Mile-Ohm, 522. 
Military telegraph, 363. 
Milliampere, 6. 
Miscellaneous, 559. 
Mirror receiver, galvanometer, 268. 
Mixed iron and hard-drawn copper wire lines, 548. 
Moment of no-magnetism, 201, 225. 

" '* methods of obviating, 

204, 228. 
Morse telegraph system, 50. 
" alphabet, 56. 

" apparatus, 58. 

" keys, See Keys. 

" operation of, 52. 

'• registers. See Registers. 

" relays. See Relays, 

single circuit or wire, 54, 173. 
" sounders, See Sounders. 

Motor governor, Phelps, 420. 

" printing telegraph, Phelps, 419. 
" push and pull, 408. 
Municipal police patrol telegraph, 488. 
Muirhead artificial cable, 279. 

double block, 279. 
Multiple break- wheel, 468, 480. 

call boxes, 373, 472, 485. 
« cells in, 24. 
•• telegraph wires in. 30. 
" transmitter, automatic, 476. 
" repeaters. See Repeaters. 
Multiplex telegraphy, synchronous, 336. 
Mutual induction between wires, electro-magnetic, 
electro-static, 99, 100. 

Negative electricity, 3, 91. 
" plate, pole, 10. 
" potential, 4. 
Neutral relay, Freir's. 225. 
Healy's, 228. 
Jones', 226. 
" resistance of, 239, 5'4. 

" three-coil, winding of, 215. 

New York Quotation Co., ticker system, 412. 

" " " quadruplex, 228. 

Nomenclature, quadruplex, 231. 

iron and steel wire, 522. 
Non-interfering automatic repeater, Gamewell, 
440. 
" fire alarm telegraph boxes, 439, 

444, 446, 449, 453. 

"Oface "wire, 79. 
Ohm, 5, 522. 

" weight per mile, 522. 
Ohm's law, 5, 25. 26, 31, 68, 112. 
Oil, battery, 14, 21, 238, 554. 
Okonite cable, 526. 
One wire ticker system, 395, 402. 
Open circuit cells, 10. 

•' method of telegraphing, 54, 

Ovei'land telegraph wire. See Telegraph Wire. 
Overlapping block signal systeu., 504. 
Oxides, peroxides, 10. 

Pad or platen, printing, 395. 

Paddle, 533. 

Page and line chemical recorder, 294. 

printer. Essick's, 430. 
Paper, chemically prepared, 291. 

feeds, 404, 418, 428. 

perforated, 296, 459. ^ 

winder, automatic, 71, 
Parallel quad, circuits, 238. 



I 



P Q 

Parallelogram of force.", 105. 

Partial resistance of telegraph wires, measuring, 

145. 
Paterson cable, 526. 
" Pause " wheel, 404. 

Pearce and Jones police patrol telegraph, 482. 
Percentage conductivity. 518. 
Perforated paper, 288, 299, 459. 
Perforator, Speicher's, 457, 
WheatPtone, 297. 
Permanent magnet, lU, 184. 
Permissive block systems, 494. 
Phatitom circuits, 231. 
Plielps' motor printer, 419. 
paper feed, 402. 
" shitting device, 403. 
" stock printer, 402. 
" synchronizing device, 427. 
" unison device, 406, 427. 
Phillips steno-telegraphy, 57a. 
Phone, 353. 

Phonoplex, Edison, 353. 
Physiologicftl telegraph, VII. 
Pin plug, 79. 
Pins, 537. 
Pikes, 535. 

Plate, positive, negative, 10, 
Platinum contact points, 59, 
Pliers, 546, 

Plug, pin, split, 79, 83, 84. 
"Plunger," 506. 
Pocket wire gauge, 515. 

relay, 64. 
Point to point method of locating faults, 530. 
Polar duplex, 181. 

" balancing, 189. 

Polarity of magnets, 181, 202. 
Polarized relays, 184, 318, 393, 554. 
Polarization, 10, 12, 17, 20. 
Pole, positive, negative, 10, 
Pole-changer, 182, 412, 431, 553. 
dynamo, 192, 225. 
Pole-changing keys, 341. 
Poles, 532. 
" erection of, etc., 532. 
" Iron, 532, 

" lightning arrester, 536. 
Police signal telegraph, 471. 

'• •' Chicago, 479. 

'« •' Game well, 472. 

" " Municipal, 488. 

«« " Pearce and Jones, 482. 

boxes, 477, 481, 493. 
Positive electricity, 3, 91. 
" pole or plate, 10, 
•* potential, 40, 
Post-auger, 533. 

Post ofBc e pattern Wheatstone bridge, 128. 
Postal arrangement of dynamo-machines, 46. 

" quadruplex, 226. 
Potential, negative, positive, 4. 
'• electro-chemical, 10. 

'* fall or slope of, 96, 122. 
Press-magnets, 393. 

relays, 415. 
Prices of telegraph apparatus, etc., 560. 
Printing telegraphy, 391. 

" telegraph circuits, adjusting, 401,429. 
" ♦' Edison, or universal. 406. 

" " Essick page and line, 430. 

" " Gold and Stock or Bcott, 395. 

" " Phelps* motor. 419. 

" " New York quotation, 412. 

" " step by step, 391, 408. 

Printing pad or platen, 395. 
Pulsatory currents, 265. 

current signals, 351. 
"Push and pull" motor, 384, 407. 
" Push " Jack, 480. 

Quadruplex telegraph, 194, 225,228. 
" balancing the, 232. 

" lightning aries er. 

" locating faults in the, 232. 

" New York Quotation Co,. 228. 

" nomenclature, 232. 

Postal, 226. 
** rei)ea,ters, See Repeaters. 



Q K 
Quadruplex, working of, etc., rules concerning, ?39. 

Railway crossing signal. Hall's electric, 503, 
electric block signal system, 494. 
" " " clock, 499. 

" " " electro pneuma- 

tic, 495. 
«« " " Hall's, 499. 

** " " overlapping, 504. 

« " " Sykes, 506, 

«« " " Union Swi tell and 

Signal, 495. 
Railroad velocipede, 550. 
Ratio of bridge arms, 519. 

" current strength, etc., 207, 217. 
Readings, galvanometer, 529. 
Receiver, Denison, 322. 
" mirror, 268. 

" Robertson, 326. 

" telephone, 344. 
" Wheatstone, 393. 
Reciprocals, 28, 518, 521. 
Recorder, siphon, 269, 271. 

'♦ chemical, 294, 
Reflecting galvanometer, 114, 519. 
Register, double-pen, 372, 
ink recording. 69. 
" Morse, 69. 

self-starting, 373, 488. 
Regular rheostat, 554. 
Relay, Brown and Allen, 281, 
•• correcting, 338. 
" differential, 170, 
" double-balance, 387. 
«' Interlocking, 503, 
" Morse, box, main-line, pocket, pony, 63, 64, 

65, 553. 
" '« adjusting, 63. 

** neutral. See Neutral R^lay, 
«* polarized, 184, 225, 318, 393, 554, 
« press, 415, 
" repeating, 416. 
« " shift," 395, 401. 
" " time," 416. 
« Wheatstone, adjusting, 304. 
'* " polaiized, 3 8. 

«♦ " repeater, 317. 

« winding of, 69, 215, 
Release magnets, 384, 416, 
"Repeat" key, 398, 
Repeaters, automatic telegraph, 153, 

" " " Maver-Gardanier,160 

" " " MUliken, 156. 

" " " Neilson, 162. 

" Side," 158. 
•« " " Toye, 158. 

« '• " multiple, 166. 

•• duplex and quadruplex, 241, 263 
" quadruplex— short wire, Downer, 244. 
** " " Gardanier, 245. 

" " " Maver multiple, 

248. 
" quadruplex— short wire, Moffatt emer- 
gency, 247. 
" quadruplex— single wire, Eiwards', 250. 
" " " hints on man 

agement of, 254. 
" quadruplex — single wire, Waterbury, 252. 
" fire alarm telegraph, Gamewell, 440. 
«' " •' manual, 454. 

" on one base-board, 167. 
" Wheatstone duplex. 307, 315. 
Repeating sounder, 215. 
Resonator, Bunnell sounder, 75, 
Resistance, 5. 

added, 231, 
box. coils, 42, 101, 174. 
" external, internal, total, 15. 

•• inversely proportional to square o" 

diameter, 'LSI. 
" joint. 27, 142, 146, 

" measurement of. See Measuring Resist- 

ance, 
•* of batterie", internal, 15. 

•* specific, 518. 

Resultant force, 103. 

" line or diagonal, 104. 
Retardation of signals, 283, 342. 



R S 
Retarding coils. 177. 

Keturn signal boxes, -See " Answer Back " Signals. 
Retractile springs, 63. 
Reversals, distant, 201, 231. 
Reversing key, 269. 

" switch, 42. 

Rheostat, 101, lU, 318. 

" combination, 214, 553. 

dial. 317. 
" regular, 554, 

Rights of way. 532. 
River and harbor cables, 528. 
Robertson writing telegraph, 325, 
Ronald's alphabetical telegraph, VI. 
Redding underg-ound conduits, 525, 
Rubber compound insulations, 529, 530, 

India, effects of high temperatures on, 560, 

Safety underground cable, 526. 

" magnet, 384. 
Sag, 544, 
Silts, 9. 

creeping, white, 14, 
Scott ticker, 395. 

" unison device, 401. 
Sc-apings, copper, zinc, 16. 
Second, 8. 

Segments, live, dead, 338. 
Segmental wheel, 392. 
S*»lf-closing key, 61. 
" exciting machines, 39. 
♦' induction, 100, 318. 

starting, self-stopping mechanism, 373. 
'" " " register, 459. 

Semaphores, XII, 495. 
Sender, automatic telegraph, 71. 
Series, cells in, 23. 

" condensers in, 94, 
Shift relays, 39c. 401. 
Shifting devices, 395, 401, 405, 416, 418. 
Short-circuit, lU. 
Sliort-circuiting key, 530, 
Shovels, long, ^poon, 533. 
Shunts, galvanometer, 116, 519, 
Shunt wound machines, 39. 
Side-guy. 526. 

" repeaters, 158. 
Siemens- Wheatstiine bridge, 130. 
Sieurs duplex, 266o. 
Signal, train order, 500. 

" branch office, 256. 
Signaling, speed of, 153, 267, 281, 287. 
torch, 365. 
" wig-wag, 363. 

Simplex cable Avorking, 276. 
Simultaneous telegraphy and telephony, 345. 
Single current method, 183, 287. 
" transmitter, 176, 553. 
" wire or circuit, 54, 173, 
Siphon recorder, Thomson, 269, 
Cuttriss, 270. 
" alphabet, 273, 

Slack In telegraph wire, 548. 
Sleeve joints, Helvin, Mclntyre, 545, 548, 549, 
Slopeor fall of potential, 96, 122. 
Smith arrange-jient of condenser, 204, 216. 
Solid conduits, 524. 

Sounders, Morse, Bunnell, main line, Victor, West- 
eru-Electric, 66, 67, 69, 553, 
•* ampere turns of, 69. 

" local, 67. 

" repeating, 215, 

" windiug of, 69. 

Special signal apparatus, police signal telegraphs, 
475, 487. 
wheel, 480, 485. 
Spacing current, 304. 
Span, wire-span, 537. 
Spark coil, 177. 
Specific gravity, 518. 

" inductive capacity, 91, 267, 
" resistance, 518. 
Specifications for apparatus, cabl«»s, wire, 553, 557. 
Specimen slip, siphon recorder, 273. 
ticker, 437, 
" writing telegraph, 327. 
Speicher's auxiliary fire alarm box, 445. 
" fire alarm telegraph, l';6. 



S T 
Split plug. 83, 

" condenser, 315. 
Spider wire, 87. 

Spinning jenny, Chinnocks, 552. 
Spring-jack, 78, 554. 

" switch -boards, 79. 

Stable outfit, police lelegra])hy, 475. 
Standard breaking strain, 522. 
" for telegraph wire. 522. 
" underground cable, 526, 
" wire gauge, 514. 
Static capacity, 91, ^67. 
" charge. 94, 97, 210. 

" compensating condensers, 177, 209, 303. 
" electricity, 90. 
Stearns' arrangement of condenser, 232, 
" artifical cable, 276, 
" duplex, 174. 
Step by step printing telegraph, 391, 408. 
Steiner key, 60. 
Steno-telegraphy, 57 a. 
Stewart-Hall train order, 506, 
Stock printer, Phelps, 402. 
Stover's special signal, 487. 
Straps, switch, 77. 
Strap keys. 484, 
Struts, 537. 

Sub-aqueous cables, 531. 
Submarine telegraphy, 267, 
Substitution method of measuring resistance, 13\ 

145, 
Subsidiary ducts, 525. 
Subway manholes, 526. 
Sulphate of copper. 12, 

" zinc, 14, 
Sunflower, 412, 
Switch, dynamo reversing, 42, 

" loop, 261. 
Switch boards, 77, 

" main ofBce, 78, 

«' way-offi2e, 81. 

" district service, 376. 

Synchronized clocks, 358. 
Synchronizing devices, 338, 427. 
Synchronous telegraphy, 336. 
Syringe, battery, 13. 

Tables, 121, 521, 562, 563. 

" concerning copper wire, 563. 
Tailings, 288. 
Tamping bar, 533, 535. 
Tapper key, 269. 
Tangent, tables of, 104, 121. 
" galvanometer, 103, 

law of, 104, 109. 
Telegraph alphabets and codes. See Alphabets. 
'• apparatus, Morse, 58. 

cables. 526. 
" lines, construction and maintenance of. 
532. 
military, 363. 
" Morse, tiee Morse Telegraph, 
" physiological, VII. 
•« repeaters. See Repeaters. 
•' Ronald's alphabetical, VI, 
" sender, automatic, 71. 
•* service, American District, 367. 
" systems. See Telegraphy. 
" transmitters, 72, 75. 

Washington's, VI, 
" wire, impurities in, 518. 
♦' " manufacture of, 511, 

" " mechanical tests of, 51», 516, 517. 

" ♦' overland, etc., 509. 

♦' " specifications for, 556. 

" wires, escapes on, 150. 
" " joint resistance of, 30, 146. 

*' •* in multiple, 30. 

" " locating faults in, See Electrical 

Testing. 
" " measuring partial insulation resist- 

ance of, 146. 
Telegraphing from moving train?, 3.33. 
Telegraphy, automatic, >'re Automatic Telegraphy, 
" automatic burglar alarm. See Burglar 

Alarm Telegraphy. 
" duplex, See Duplex Telegraphy, 

" fac simile, 321, 



Telegraphy, fire alarm. See Fire Alarm Telegraphy. 
" multiplex. AfeeSyuchronuus Telegraph 

Systems. 
police signal. See Police Signal Tele- 
graph Systems. 
" printing. See Printing Telegraphy. 

«• quadruplex. See Quadruples. 

«* steno, 57«. 

«« submarine, 267, 

«« synchronous multiplex, 336. 

" typewriter In, 74. 

* undor-water, 285. 

Telephone, the, 344. 

" •« in automatic telegraphy, 294. 

" " " police signal telegraphy, 474. 

" terminal connections of, 350. 

*' transmitter, receiver, 344. 

Temperature, effects of on liquids, on conductors, 
16, 520, 560. 
corrections for, 520. 
Tensile strength, 516, 522, 514. 
Terms, chemical. 9. 
" electrical, 3. 
Test, Varley loop test, 140. 
Testing, electrical, 122, 519. 

" the condition of batteries, 134. 
•• " ' relays, 236. 

" insulators, 148. 
Testometer, " 386. 

Tests, capacity, 131. 

" mechanical, See Mechanical Tests. 
" of telegraph wire, See Electrical, Mechanical 
Tests. 
The quadruplex, See Quadruplex. 
Thomson's reflecting gali^anometer, 114. 
" Throwing out," 394. 
Tickers, 394. 

" Edison, two wire, 406. 
" Essick, 436. 

" Gold and Stock, or Scott two wire, 40L 
" Kiernan " news," 391. 
" New York Quotation Co., 412, 416. 
'* Phelps, one wire, 405. • 
«« slip, specimen of, 436. 
Tie, Helvin, 544. 

" wire, 544. 
Time slips, 379. 

" stamp, 471, 474, 480. 
" telegraph service, 356. 
Tools used in construction of telegraph lines, 533. 
Tooker keyless door, 493. 
Torch signaling, 365. 
Tower-bell circuits, 456. 

" striking mechanism, 461. 
Track instrument. Hall's, 500. 
Train order signal, 506. 
Train signal, 507. 
Trailer, 336, 341, 412. 

Transmitter, continuity preserving, 176, 353, 
" Denison, 322. 

*« Etheridge, 327. 

*« Healy, 412. 

•* key-board, 392. 

•* multiple automatic, 476. 

•• Morse telegraph, 72. 

'• Phelps' motor, 422. 

" phonoplex, 353. 

priming telegraph, 392, 398, 407, 411, 
412, 421, 430. 
" Robertson. 

Tree insulator, .542. 
■=' trimmer. 549. 



T U V W Z 

Trouble " hunting," 551. 

Two type-wheel tickers, 395. 

Tying wire to insulators, 544. 

Type-wheels, 391, 395. 

Type- writer in telegraphy, 74, 76. 

Underground conduits for cables, 524. 

" " drawing in aud out, 594. 

Edison, solifl,524. 
" " Johnstone, 526. 

" telegraph cables, Kerite, Okonite, 

Paterson, Safety, Standard, 526. 
Under-running of cables, 531. 
Union Switch and Signal electro-pneumatic block. 

system, 495. 
Union Switch and Signal clock block signals, 499. 
Unit, B. A., 522. 
Units, electrical, 7. 

C. G. S., 8. 
United States signal and telegraph code, 363. 
Unison devices, 395, 401, 406, 427. 
Universal ticker, transmitter, 406, 410. 

VanRysselberghe simultaneous telegraphy and 

telephony, 345. 
VanSize return signal box, 370. 
Variable zero, 273, 283. 
Varley loop test, 140, 530. 
Varley-Athearn duplex, 351. 
Velocipede, railroad, 550. 
Victor key, 58. 
Vulcanized India rubber, effects of high tempera. 

tures on, 560. 

Way leaves. 532. 

Way office, 54. 

Weight per mile ohm, 522, 523. 

Western Union arrangement of dynamo machinas- 

44. 
Wheatstone automatic telegraph system, 296. 
bridge, 122, 126, 128, 519. 
circuits, lengths of, 321. 
•* condenser, 93. 

duplex, 305. 
" perforator, receiver, relay, repeater^i 

transmitter, 296, 298, 303, 306. 
White salts, 14. 

Wig-wag method of signaling, 363. 
Wilder "duplex " auto, burglar alarm, 383. 
" Wind and water" line, 533. 
Winding of three-coil neutral relay, 215. 
" " relays and sounders, 65, 69. 

Wire barrow, 543. 
" method of placing on poles, 542. 
" compound copper and steel, etc., 510. 
" diameter of, 281, 514. 
*' drawing, 511. 
" elongation of, 510. 
«« gauges, 514, 515, 562. 
" " office," 70. 
** overland telegraph, 509. 
'* stringing, 542. 
Wires, See Telegraph Wires, 
Working constant of galvanometer, 144. 
W. U. insulator, 539. 



Zero, variable, 273, 283. 
Zinc and copper scraper, 555. 

" crowfoot, 12. 

" scrapings, 16. 
Zincs amalgamation of, 18. 



Wireless Telegraphy : 

Theory and Practice. 

BY 

William Maver, Jr. 

Over 200 pages and 123 illustrations. 

Embracing Early Wireless Telegraph Systems. In- 
duction Telegraphy. Hertzian Waves. Electromag- 
netic Theory of Light. Electronic Theory. Theories 
of Propagation of Electric Waves. Syntonic Wireless 
Telegraphy. Wireless Telegraph Systems of Marconi, 
Lodge and Muirhead, Slaby-Arco, Braun, Branly-Popp, 
Guarini, Ducretet-Poppoff, De Forest, Fessenden, Stone, 
Shoemaker, Ehret, Bull, Musso, Armorl, etc., etc. Tele- 
graphing by Ultra Violet Waves. Wireless Telephone 
Systems of Bell, Ruhmer, Hays, Collins. Speaking Arc, 
Speaking Light, etc. Sections on Detectors, Coherers, 
Spark Gap, Interrupters, Aerial Wires, etc. 

Sent to any part of the world, postage prepaid, on 
receipt of price, $3.00. 

Any other Electrical Book Supplied^ 

MAVER PUBLISHING CO., 

Liberty Street . =. . New York. 



MAVER ELECTRICAL SUPPLY CO. 

136 Liberty Street, New York. 
Wireless Telegraph Apparatus for Practical and Experimental Use. 



Four and eight- inch spark induction coils with Morse key and 
oscillator, .foo to $125. 

Complete receiver with high resistance relay, vibrating bell and 
adjustable coherer. $15.00. 

Complete experimental portable transmitter in polished oak-box, 
about six inches square, provided with spark coil, oscillator, 
Morse key, batteries and antenna. Antenna about 10 feet 
high, consisting of jointed aluminum tubes. Transmits about 
100 feet. Apparatus, $25 00. Antenna, $3.00. 

Sensitive adjustable coherer with choke coils. $5.00. 

Two telephone receivers, 750 ohms each, attached to adjustable 
head band, with connecting cords. $15 00. 

Special insulators for top and bottom of wire antennae. $1.00. 

Platinum wire .00006 inch diameter with silver coat, in lengths of 
one foot or more. Specially drawn for experimental work 
with electrolytic detectors, etc. Per foot, $3.00. 

The induction coils are of special and superior construction. The 
primary and secondary wires are respectively made in detach- 
able sections ; can be connected in series, series multiple, or 
straight series for use with different spark lengths and spark 
volume; are well adapted to experimental work. The coils 
can also be used as high tension transformers with alterna- 
ting current. (Above prices subject to change.) 

ELECTRICAL APPARATUS AND SUPPLIES, WET AND DRY BATTERIES^ ETC. 



WM. MAVER, Jr. 

Consulting Electrical Engineer. Member Am. Inst. Elec. Engineers, 
136 LIBERTY STREET, NEW YORK. 



Investigations and Reports on Telegraphy. Telephony, Wireless Teleg- 
raphy and Telephony, Insulating Materials, Wires, Underground Cables and 
Conduits, etc. 



FOR OVER TWENTY YEARS THE NAME 

"BUNNELL' 

ON TELEGRAPH INSTRUMENTS 

has been recognized as a guarantee of highest grade of material and workmanship. 
The aim of this house is to manufacture the best of everything in the tele- 
graph line, mechanically as well as scientifically. 



BUNNELL STANDARD RELAY WITH LATEST IMPROVEMENTS. 

We furnish complete equipments of 

KEYS, RELAYS, SOUNDERS, REGISTERS, SWITCHES, 

LIGHTNING ARRESTERS, BATTERIES, 
REPEATERS, DUPLEX AND QUADRUPLEX OUTFITS, 

ETC., ETC. 

District Call Boxes and Inking Registers 

A SPECIALTY. 

We carry a large stock of Tools and Line Material, such as Wire, Insu- 
lators, Pins, Brackets, Braces, etc., etc. 

Our many years' experience is at the service of our customers. Orders solicited. 
Satisfaction promised. Catalogues free on request. 

J. R BUNNELL & CO,, Inc 

Manufacturers of Electrical Apparatus, 

Main Office: 20 PARK PLACE, NEW YORK. 

P. O. Box, 12S6. Cable Address, "-Bunnell." 



^:^ ^^.. 






A 






'<' , "-5^^ 



'3 



^1 



v^~ 




.^^^ *'i/^ 



O 0" 



r-:cf« 



^? 



.° K^^ '<--. *, 






^," ^je?_:J^ 






^^ 



c 






oX- 






^. %^' 



^^: v,^^- 



, o . 



x^--^ 






</> \ 



,/v: 












^;- ,^?^ ^ 



,y ^^- 




<f <\ 












A. - 



-0' -o, 



^"^ <^^ 



\v ^> 



^^:^^Pr ./ ^' 



O. V 









.^.0^ 



1 o 



.0^ 



"oo^ 






^^% ^^ ^ 






:# v^i:^'^ A 



N o ^ * ^ -", 



X^^^. 



'^'^^" : 



-^ ^J^^Pr' cV'^ 







x-^ 4.0^ 















^'^ 









v 




'■^/f\^i\^ : 



^^^>.^ 






"t^v^ 



s ^ ^' *' / 



s o > x'^ 



■A" -■/-. 



LIBRARY OF CONGRESS 



021 094 321 ? 



